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Stainless Steel Duolok Tube Fitting, 0.25 Inch Tube OD Union

Description & Features

Stainless Steel Duolok Tube Fitting 0.25 Inch Tube OD Union offers a reliable leak-proof connection in instrumentation and process tubing systems. The double ferrule design adjusts for variations in tubing materials hardness and tube wall thickness ensuring leak-tight connections across diverse applications.

Duolok tube fittings are crafted from type 316 stainless steel per ASTM A-276 and ASTM A-479 standards with shaped bodies from close-grained 316 stainless steel forgings per ASTM A-182. All components are heat code traceable and certified material test reports (CMTRs) are available.

These fittings are engineered to be gaugeable enhancing initial installation precision. Duolok tube fittings are designed for full interchangeability with Swagelok brand tube fittings.

Generally rated for the maximum allowable working pressures of the recommended stainless steel tubing some specialized fittings may have lower pressure ratings. They operate reliably over a broad range of temperatures although elevated temperatures will reduce the maximum working pressure capacity.

For detailed assembly instructions and safety information regarding proper selection of tubing and tube fittings contact us directly.

Supplier Part Number: ISSD4U

Specifications

A 1.61	B 1.03	E 0.19	Brand Ssp Fittings Corp	Brand SSP Fittings Corp	Pack Size 1.00	UOM EA	Supplier Part Number ISSD4U	T 0.25	Alternate Part Numbers Alternate Part Number C1FP17, Alternate Part Number MI-08419237, Alternate Part Number MINO-00766X52400	Product Weight 0.08 lbs

Similar Products

Model Number	T	A	B	E	Price	Action
ISSD4U Stainless Duolok Tube Union	0.25	1.61	1.03	0.19
ISSD6U Stainless Duolok Tube Union	0.38	1.77	1.19	0.28

Product Questions & Answers (3)

Question by: Earl F on Jul 4, 2025, 4:06 PM

these swap out direct with Swagelok fittings, or do I need to change anything else out when I switch over?

Answer by: Customer Support on Jul 6, 2025, 9:38 AM

Full interchangeability with Swagelok brand fittings is built into the Duolok design, so you can swap them in without modifying the surrounding hardware. The dimensions and double ferrule system are controlled to match, which is part of why gageability is built in as well. That gaugeability feature also helps confirm you've got enough pull-up on initial installation, so you're not left guessing whether the connection seated right.

Question by: Harold P on Feb 12, 2026, 12:24 PM

What kind of pressure rating can I expect from this union when used with stainless steel tubing?

Answer by: Customer Support on Feb 14, 2026, 6:16 AM

Generally, these Duolok tube fittings are rated for pressures equal to the maximum allowable working pressures of the stainless steel tubing recommended for use with them. Keep in mind that some specially designed fittings may have a lower pressure rating than the tubing itself.

Question by: Kirk H on Aug 21, 2025, 8:20 AM

got a 1/4 inch stainless instrument tube run. is this the union that just joins two tubes together?

Answer by: Customer Support on Aug 22, 2025, 9:51 AM

Use it when you need a straight union to connect two pieces of 0.25 inch OD tubing in an instrumentation or process tubing line. It uses a double ferrule setup that helps seal up even when tube wall thickness or hardness varies.