2103-257 PTFE S/T BUP FDA

TST257 is an AS568-257 white PTFE (Teflon) 55 Shore D Back-Up Ring built to an inside diameter of 5.859 in (148.82 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 6.137 in (155.88 mm). In service, this back-up ring extends o-ring service life by supporting the seal against extrusion under high pressure.

As a material, PTFE (Teflon) delivers near-universal chemical inertness and one of the lowest coefficients of friction of any solid. The material holds up against oxidizing media, nearly all industrial chemicals, and steam. Service temperature is rated from -65°F (-53.9°C) through 500°F (260°C). Exposure to elemental fluorine at temperature or molten alkali metals will shorten service life.

Maintenance and OEM teams specify it across pharmaceutical and biotech, laboratory equipment, and chemical processing.

Reference part number TST257 when ordering; the item is sold individually. Nominal inside diameter is listed as 5 7/8 inch. As always, verify media compatibility and operating conditions against the requirements of your specific application. APG supports cross-referencing from drawings, samples and competitor numbers when a listed size is not an exact fit.