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Polyurethane U-Seal, 3.50 Inch OD, 3.13 Inch ID, 0.38 Inch Height

Description & Features

Manufactured by Hercules Sealing Products, this polyurethane U-seal is designed for hydraulic cylinder and linear actuator applications where reliable rod or piston sealing is required. The beveled lip design promotes effective fluid film control across a wide range of operating conditions.

The Polyurethane U-Seal, 3.50 Inch OD, 3.13 Inch ID, 0.38 Inch Height features a height greater than its cross section, classifying it as a deep-type profile. Urethane construction supports a pressure range of 0 to 6,000 PSI and a temperature range of -65°F to 220°F, making it well-suited for demanding hydraulic environments.

SKU: U18-3.12-37B

Supplier Part Number (MPN): U18-3.12-37B

Alternate Part Numbers: C1DN81

Specifications

Cross Section 0.1875 in	Brand Hercules Sealing Products	Brand Hercules Sealing Products	Pack Size 1.00	UOM EA	H 0.375 in	I.D. 3.125 in	O.D. 3.5 in	Supplier Part Number U18-3.12-37B	Alternate Part Numbers Alternate Part Number C1DN81	Product Weight 0.04 lbs

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Model Number	Cross Section	I.D.	O.D.	H
U12-0.62-25B Polyurethane U-Seal	0.125 in	0.625 in	0.875 in	0.25 in
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U18-1.25-SQB Polyurethane U-Seal	0.1875 in	1.25 in	1.625 in	0.1875 in
U18-1.75-37B Polyurethane U-Seal	0.1875 in	1.75 in	2.125 in	0.375 in
U18-2.12-SQB Polyurethane U-Seal	0.1875 in	2.125 in	2.5 in	0.1875 in
U18-2.50-31B Polyurethane U-Seal	0.1875 in	2.5 in	2.875 in	0.3125 in
U25-1.25-37B Polyurethane U-Seal	0.25 in	1.25 in	1.75 in	0.375 in
U25-1.50-37B Polyurethane U-Seal	0.25 in	1.5 in	2 in	0.375 in
U25-2.00-37B Polyurethane U-Seal	0.25 in	2 in	2.5 in	0.375 in
U25-2.50-37B Polyurethane U-Seal	0.25 in	2.5 in	3 in	0.375 in
U25-3.00 Polyurethane U-Seal	0.25 in	3 in	3.5 in	0.25 in
U25-3.00-37B Polyurethane U-Seal	0.25 in	3 in	3.5 in	0.375 in
U25-3.50-37B Polyurethane U-Seal	0.25 in	3.5 in	4 in	0.375 in
U25-4.00-SQB Polyurethane U-Seal	0.25 in	4 in	4.5 in	0.25 in
U25-4.50 Polyurethane U-Seal	0.25 in	4.5 in	5 in	0.25 in
U25-5.00 Polyurethane U-Seal	0.25 in	5 in	5.5 in	0.25 in
U12-0.18-25B Polyurethane U-Seal	0.125 in	0.1875 in	0.438 in	0.25 in
U12-0.25-25B Polyurethane U-Seal	0.125 in	0.25 in	0.5 in	0.25 in
U12-0.25-SQB Polyurethane U-Seal	0.125 in	0.25 in	0.5 in	0.125 in
U12-0.31-25B Polyurethane U-Seal	0.125 in	0.3125 in	0.563 in	0.25 in
U12-0.31-SQB Polyurethane U-Seal	0.125 in	0.3125 in	0.563 in	0.125 in
U12-0.37 Polyurethane U-Seal	0.125 in	0.375 in	0.625 in	0.125 in
U12-0.50-25B Polyurethane U-Seal	0.125 in	0.5 in	0.75 in	0.25 in
U12-0.50-SQB Polyurethane U-Seal	0.125 in	0.5 in	0.75 in	0.125 in
U12-0.56 Polyurethane U-Seal	0.125 in	0.625 in	0.938 in	0.125 in
U12-0.62-SQB Polyurethane U-Seal	0.125 in	0.625 in	0.875 in	0.125 in
U12-0.68 Polyurethane U-Seal	0.125 in	0.6875 in	0.938 in	0.125 in
U12-0.75-18B Polyurethane U-Seal	0.125 in	0.75 in	1 in	0.1875 in
U12-0.75-25B Polyurethane U-Seal	0.125 in	0.75 in	1 in	0.25 in
U12-0.75-SQB Polyurethane U-Seal	0.125 in	0.75 in	1 in	0.125 in
U12-0.81 Polyurethane U-Seal	0.125 in	0.8125 in	1.063 in	0.125 in
U12-0.87-25B Polyurethane U-Seal	0.125 in	0.875 in	1.125 in	0.25 in
U12-0.87-SQB Polyurethane U-Seal	0.125 in	0.875 in	1.125 in	0.125 in
U12-1.00-18B Polyurethane U-Seal	0.125 in	1 in	1.25 in	0.1875 in
U12-1.00-SQB Polyurethane U-Seal	0.125 in	1 in	1.25 in	0.125 in
U12-1.06-SQB Polyurethane U-Seal	0.125 in	1.0625 in	1.313 in	0.125 in
U12-1.12-25B Polyurethane U-Seal	0.125 in	1.0625 in	1.375 in	0.25 in
U12-1.12-SQB Polyurethane U-Seal	0.125 in	1.0625 in	1.375 in	0.125 in
U12-1.18 Polyurethane U-Seal	0.125 in	0.188 in	1.438 in	0.125 in
U12-1.18-18B Polyurethane U-Seal	0.125 in	0.188 in	1.438 in	0.1875 in
U12-1.18-25B Polyurethane U-Seal	0.125 in	0.188 in	1.438 in	0.25 in
U12-1.25-18B Polyurethane U-Seal	0.125 in	1.25 in	1.5 in	0.1875 in
U12-1.25-25B Polyurethane U-Seal	0.125 in	1.25 in	1.5 in	0.25 in
U12-1.37-25B Polyurethane U-Seal	0.125 in	1.375 in	1.625 in	0.25 in
U12-1.37-SQB Polyurethane U-Seal	0.125 in	1.375 in	1.625 in	0.125 in
U12-1.50-25B Polyurethane U-Seal	0.125 in	1.5 in	1.75 in	0.25 in
U12-1.50-SQB Polyurethane U-Seal	0.125 in	1.5 in	1.75 in	0.125 in
U12-1.62-SQB Polyurethane U-Seal	0.125 in	1.625 in	1.875 in	0.125 in
U12-1.75-SQB Polyurethane U-Seal	0.125 in	1.75 in	2 in	0.125 in
U12-2.00 Polyurethane U-Seal	0.125 in	2 in	2.25 in	0.125 in
U12-2.25 Polyurethane U-Seal	0.125 in	2.25 in	2.5 in	0.125 in
U12-2.75 Polyurethane U-Seal	0.125 in	2.75 in	3 in	0.125 in
U15-1.18 Polyurethane U-Seal	0.1563 in	0.188 in	1.5 in	0.1563 in
U15-1.25 Polyurethane U-Seal	0.1563 in	1.25 in	1.563 in	0.1563 in
U15-1.37 Polyurethane U-Seal	0.1563 in	1.375 in	1.688 in	0.1563 in
U18-0.50 Polyurethane U-Seal	0.1875 in	0.5 in	0.875 in	0.1875 in
U18-0.62-31B Polyurethane U-Seal	0.1875 in	0.625 in	1 in	0.3125 in
U18-0.62-SQB Polyurethane U-Seal	0.1875 in	0.625 in	1 in	0.1875 in
U18-0.75-31B Polyurethane U-Seal	0.1875 in	0.75 in	1.125 in	0.3125 in
U18-0.75-SQB Polyurethane U-Seal	0.1875 in	0.75 in	1.125 in	0.1875 in
U18-0.87-31B Polyurethane U-Seal	0.1875 in	0.875 in	1.25 in	0.3125 in
U18-0.87-SQB Polyurethane U-Seal	0.1875 in	0.875 in	1.25 in	0.1875 in
U18-1.00-25B Polyurethane U-Seal	0.1875 in	1 in	1.375 in	0.25 in
U18-1.00-31B Polyurethane U-Seal	0.1875 in	1 in	1.375 in	0.3125 in
U18-1.00-37B Polyurethane U-Seal	0.1875 in	1 in	1.375 in	0.375 in
U18-1.00-SQB Polyurethane U-Seal	0.1875 in	1 in	1.375 in	0.1875 in
U18-1.12-25B Polyurethane U-Seal	0.1875 in	1.0625 in	1.5 in	0.25 in
U18-1.12-31B Polyurethane U-Seal	0.1875 in	1.0625 in	1.5 in	0.3125 in
U18-1.12-SQB Polyurethane U-Seal	0.1875 in	1.0625 in	1.5 in	0.1875 in
U18-1.18 Polyurethane U-Seal	0.1875 in	0.188 in	1.563 in	0.1875 in
U18-1.25-25B Polyurethane U-Seal	0.1875 in	1.25 in	1.625 in	0.25 in
U18-1.25-31B Polyurethane U-Seal	0.1875 in	1.25 in	1.625 in	0.3125 in
U18-1.25-37B Polyurethane U-Seal	0.1875 in	1.25 in	1.625 in	0.375 in
U18-1.37-25B Polyurethane U-Seal	0.1875 in	1.375 in	1.75 in	0.25 in
U18-1.37-31B Polyurethane U-Seal	0.1875 in	1.375 in	1.75 in	0.3125 in
U18-1.37-37B Polyurethane U-Seal	0.1875 in	1.375 in	1.75 in	0.375 in
U18-1.37-SQB Polyurethane U-Seal	0.1875 in	1.375 in	1.75 in	0.1875 in
U18-1.50-25B Polyurethane U-Seal	0.1875 in	1.5 in	1.875 in	0.25 in
U18-1.50-31B Polyurethane U-Seal	0.1875 in	1.5 in	1.875 in	0.3125 in
U18-1.50-37B Polyurethane U-Seal	0.1875 in	1.5 in	1.875 in	0.375 in
U18-1.50-SQB Polyurethane U-Seal	0.1875 in	1.5 in	1.875 in	0.1875 in
U18-1.62 Polyurethane U-Seal	0.1875 in	1.625 in	2 in	0.1875 in
U18-1.62-25B Polyurethane U-Seal	0.1875 in	1.625 in	2 in	0.25 in
U18-1.62-31B Polyurethane U-Seal	0.1875 in	1.625 in	2 in	0.3125 in
U18-1.62-37B Polyurethane U-Seal	0.1875 in	1.625 in	2 in	0.375 in
U18-1.62-SQB Polyurethane U-Seal	0.1875 in	1.625 in	2 in	0.1875 in
U18-1.75-25B Polyurethane U-Seal	0.1875 in	1.75 in	2.125 in	0.25 in
U18-1.75-31B Polyurethane U-Seal	0.1875 in	1.75 in	2.125 in	0.3125 in
U18-1.75-SQB Polyurethane U-Seal	0.1875 in	1.75 in	2.125 in	0.1875 in
U18-1.87-37B Polyurethane U-Seal	0.1875 in	1.875 in	2.25 in	0.375 in
U18-1.87-SQB Polyurethane U-Seal	0.1875 in	1.875 in	2.25 in	0.1875 in
U18-2.00-31B Polyurethane U-Seal	0.1875 in	2 in	2.375 in	0.3125 in
U18-2.00-37B Polyurethane U-Seal	0.1875 in	2 in	2.375 in	0.375 in
U18-2.00-SQB Polyurethane U-Seal	0.1875 in	2 in	2.375 in	0.1875 in
U18-2.12-25B Polyurethane U-Seal	0.1875 in	2.125 in	2.5 in	0.25 in
U18-2.25-37B Polyurethane U-Seal	0.1875 in	2.25 in	2.625 in	0.375 in
U18-2.25-SQB Polyurethane U-Seal	0.1875 in	2.25 in	2.625 in	0.1875 in
U18-2.37-SQB Polyurethane U-Seal	0.1875 in	2.375 in	2.75 in	0.1875 in
U18-2.50-25B Polyurethane U-Seal	0.1875 in	2.5 in	2.875 in	0.25 in
U18-2.50-37B Polyurethane U-Seal	0.1875 in	2.5 in	2.875 in	0.375 in
U18-2.50-SQB Polyurethane U-Seal	0.1875 in	2.5 in	2.875 in	0.1875 in
U18-2.62-37B Polyurethane U-Seal	0.1875 in	2.625 in	3 in	0.375 in
U18-2.62-SQB Polyurethane U-Seal	0.1875 in	2.625 in	3 in	0.1875 in
U18-2.75-37B Polyurethane U-Seal	0.1875 in	2.75 in	3.125 in	0.375 in
U18-2.75-SQB Polyurethane U-Seal	0.1875 in	2.75 in	3.125 in	0.1875 in
U18-2.87 Polyurethane U-Seal	0.1875 in	2.875 in	3.25 in	0.1875 in
U18-3.00 Polyurethane U-Seal	0.1875 in	3 in	3.375 in	0.1875 in
U18-3.00-37B Polyurethane U-Seal	0.1875 in	3 in	3.375 in	0.375 in
U18-3.12-37B Polyurethane U-Seal	0.1875 in	3.125 in	3.5 in	0.375 in
U18-3.12-SQB Polyurethane U-Seal	0.1875 in	3.125 in	3.5 in	0.1875 in
U18-3.50-37B Polyurethane U-Seal	0.1875 in	3.5 in	3.875 in	0.375 in
U18-3.62-37B Polyurethane U-Seal	0.1875 in	3.625 in	4 in	0.375 in
U18-3.62-SQB Polyurethane U-Seal	0.1875 in	3.625 in	4 in	0.1875 in
U18-4.00-37B Polyurethane U-Seal	0.1875 in	4 in	4.375 in	0.375 in
U25-0.75 Polyurethane U-Seal	0.25 in	0.75 in	1.25 in	0.25 in
U25-0.93 Polyurethane U-Seal	0.25 in	0.8125 in	1.438 in	0.25 in
U25-1.00-37B Polyurethane U-Seal	0.25 in	1 in	1.5 in	0.375 in
U25-1.00-SQB Polyurethane U-Seal	0.25 in	1 in	1.5 in	0.25 in
U25-1.12 Polyurethane U-Seal	0.25 in	1.0625 in	1.625 in	0.25 in
U25-1.12-37B Polyurethane U-Seal	0.25 in	1.0625 in	1.625 in	0.375 in
U25-1.18 Polyurethane U-Seal	0.25 in	0.188 in	1.688 in	0.25 in
U25-1.25-SQB Polyurethane U-Seal	0.25 in	1.25 in	1.75 in	0.25 in
U25-1.37 Polyurethane U-Seal	0.25 in	1.375 in	1.875 in	0.25 in
U25-1.37-37B Polyurethane U-Seal	0.25 in	1.375 in	1.875 in	0.375 in
U25-1.50-31B Polyurethane U-Seal	0.25 in	1.5 in	2 in	0.3125 in
U25-1.50-SQB Polyurethane U-Seal	0.25 in	1.5 in	2 in	0.25 in
U25-1.75 Polyurethane U-Seal	0.25 in	1.75 in	2.25 in	0.25 in
U25-1.75-37B Polyurethane U-Seal	0.25 in	1.75 in	2.25 in	0.375 in
U25-1.87-37B Polyurethane U-Seal	0.25 in	1.875 in	2.375 in	0.375 in
U25-2.00-31B Polyurethane U-Seal	0.25 in	2 in	2.5 in	0.3125 in
U25-2.00-SQB Polyurethane U-Seal	0.25 in	2 in	2.5 in	0.25 in
U25-2.12-37B Polyurethane U-Seal	0.25 in	2.125 in	2.625 in	0.375 in
U25-2.25 Polyurethane U-Seal	0.25 in	2.25 in	2.75 in	0.25 in
U25-2.25-37B Polyurethane U-Seal	0.25 in	2.25 in	2.75 in	0.375 in
U25-2.37-37B Polyurethane U-Seal	0.25 in	2.375 in	2.875 in	0.375 in
U25-2.50-SQB Polyurethane U-Seal	0.25 in	2.5 in	3 in	0.25 in
U25-2.62-37B Polyurethane U-Seal	0.25 in	2.625 in	3.125 in	0.375 in
U25-2.75-37B Polyurethane U-Seal	0.25 in	2.75 in	3.25 in	0.375 in
U25-2.75-SQB Polyurethane U-Seal	0.25 in	2.75 in	3.25 in	0.25 in
U25-3.25-37B Polyurethane U-Seal	0.25 in	3.25 in	3.75 in	0.375 in
U25-3.50 Polyurethane U-Seal	0.25 in	3.5 in	4 in	0.25 in
U25-3.50-SQB Polyurethane U-Seal	0.25 in	3.5 in	4 in	0.25 in
U25-3.75-37B Polyurethane U-Seal	0.25 in	3.75 in	4.25 in	0.375 in
U25-3.75-SQB Polyurethane U-Seal	0.25 in	3.75 in	4.25 in	0.25 in
U25-4.00-37B Polyurethane U-Seal	0.25 in	4 in	4.5 in	0.375 in
U25-4.00-50D Polyurethane U-Seal	0.25 in	4 in	4.5 in	0.5 in
U25-4.00-56B Polyurethane U-Seal	0.25 in	4 in	4.5 in	0.5625 in
U25-4.50-37B Polyurethane U-Seal	0.25 in	4.5 in	5 in	0.375 in
U25-4.50-56B Polyurethane U-Seal	0.25 in	4.5 in	5 in	0.5625 in
U25-4.50-62B Polyurethane U-Seal	0.25 in	4.5 in	5 in	0.625 in
U25-5.00-37B Polyurethane U-Seal	0.25 in	5 in	5.5 in	0.375 in
U25-5.50 Polyurethane U-Seal	0.25 in	5.5 in	6 in	0.25 in
U25-5.50-37B Polyurethane U-Seal	0.25 in	5.5 in	6 in	0.375 in
U25-5.50-56B Polyurethane U-Seal	0.25 in	5.5 in	6 in	0.5625 in
U31-1.00-50B Polyurethane U-Seal	0.3125 in	1 in	1.625 in	0.5 in
U31-1.25 Polyurethane U-Seal	0.3125 in	1.25 in	1.875 in	0.3125 in
U31-1.25-37B Polyurethane U-Seal	0.3125 in	1.25 in	1.875 in	0.375 in
U31-1.37-37B Polyurethane U-Seal	0.3125 in	1.375 in	2 in	0.375 in
U31-1.37-SQB Polyurethane U-Seal	0.3125 in	1.375 in	2 in	0.3125 in
U31-1.50 Polyurethane U-Seal	0.3125 in	1.5 in	2.125 in	0.3125 in
U31-1.75-37B Polyurethane U-Seal	0.3125 in	1.75 in	2.375 in	0.375 in
U31-1.87 Polyurethane U-Seal	0.3125 in	1.875 in	2.5 in	0.3125 in
U31-2.00 Polyurethane U-Seal	0.3125 in	2 in	2.625 in	0.3125 in
U31-2.00-50B Polyurethane U-Seal	0.3125 in	2 in	2.625 in	0.5 in
U31-2.25-50B Polyurethane U-Seal	0.3125 in	2.25 in	2.875 in	0.5 in
U31-2.37 Polyurethane U-Seal	0.3125 in	2.375 in	3 in	0.3125 in
U31-2.50 Polyurethane U-Seal	0.3125 in	2.5 in	3.125 in	0.3125 in
U31-2.50-50B Polyurethane U-Seal	0.3125 in	2.5 in	3.125 in	0.5 in
U31-2.75 Polyurethane U-Seal	0.3125 in	2.75 in	3.375 in	0.3125 in
U31-2.75-50B Polyurethane U-Seal	0.3125 in	2.75 in	3.375 in	0.5 in
U31-2.87 Polyurethane U-Seal	0.3125 in	2.875 in	3.5 in	0.3125 in
U31-3.00-50B Polyurethane U-Seal	0.3125 in	3 in	3.625 in	0.5 in
U31-3.37-50B Polyurethane U-Seal	0.3125 in	3.375 in	4 in	0.5 in
U31-4.00 Polyurethane U-Seal	0.3125 in	4 in	4.625 in	0.3125 in
U31-4.00-56B Polyurethane U-Seal	0.3125 in	4 in	4.625 in	0.5625 in
U31-4.37 Polyurethane U-Seal	0.3125 in	4.375 in	5 in	0.3125 in
U31-4.50 Polyurethane U-Seal	0.3125 in	4.5 in	5.125 in	0.3125 in
U37-1.25 Polyurethane U-Seal	0.375 in	1.25 in	2 in	0.375 in
U37-1.75 Polyurethane U-Seal	0.375 in	1.75 in	2.5 in	0.375 in
U37-2.50-50B Polyurethane U-Seal	0.375 in	2.5 in	3.25 in	0.5 in
U37-2.75 Polyurethane U-Seal	0.375 in	2.75 in	3.5 in	0.375 in
U37-3.25-50B Polyurethane U-Seal	0.375 in	3.25 in	4 in	0.5 in
U37-3.50 Polyurethane U-Seal	0.375 in	3.5 in	4.25 in	0.375 in
U37-3.75-50D Polyurethane U-Seal	0.375 in	3.75 in	4.5 in	0.5 in
U37-4.00-62B Polyurethane U-Seal	0.375 in	4 in	4.75 in	0.625 in
U37-4.25-50D Polyurethane U-Seal	0.375 in	4.25 in	5 in	0.5 in
U37-4.25-62B Polyurethane U-Seal	0.375 in	4.25 in	5 in	0.625 in
U37-4.25-SQB Polyurethane U-Seal	0.375 in	4.25 in	5 in	0.375 in
U37-4.50-62B Polyurethane U-Seal	0.375 in	4.5 in	5.25 in	0.625 in
U37-5.00-62B Polyurethane U-Seal	0.375 in	5 in	5.75 in	0.625 in
U37-5.25 Polyurethane U-Seal	0.375 in	5.25 in	6 in	0.375 in
U37-5.25-50D Polyurethane U-Seal	0.375 in	5.25 in	6 in	0.5 in
U37-6.25-50D Polyurethane U-Seal	0.375 in	6.25 in	7 in	0.5 in
U50-2.00-SQB Polyurethane U-Seal	0.5 in	2 in	3 in	0.5 in
U50-2.50 Polyurethane U-Seal	0.5 in	2.5 in	3.5 in	0.5 in

Product Questions & Answers (2)

Question by: Clint W on Aug 13, 2025, 3:06 PM

Got a hydraulic cylinder with a 3.50 OD and 3.13 ID bore situation, this u-seal gonna fit that right up?

Answer by: Customer Support on Aug 15, 2025, 8:30 AM

Those dimensions line up exactly with what this seal is built for. The 3.50 inch OD, 3.13 inch ID, and 0.38 inch height are the hard specs, so if your cylinder matches those numbers, you're good to go. The 0.1875 inch cross section and deep-type profile mean the height runs greater than the cross section, which is worth confirming fits your gland geometry before you press it in.

Question by: Dwayne F on Sep 4, 2025, 9:06 PM

got a cylinder that takes a 3-1/8 ID seal. is this u-seal the right size or am i off a hair

Answer by: Customer Support on Sep 6, 2025, 5:04 PM

Fit comes down to the dimensions on the seal itself. This one is 3.125 inch ID, 3.50 inch OD, with a 0.375 inch height and a 0.1875 inch cross section, so it matches a 3-1/8 inch ID callout.