2103-357 PTFE S/T BUP FDA

APG stocks the TST357, an AS568-357 white PTFE (Teflon) 55 Shore D Back-Up Ring with an inside diameter of 5.475 in (139.07 mm), a cross section of 0.21 in (5.33 mm), and an outside diameter of 5.895 in (149.73 mm). A back-up ring installs on the low-pressure side of an o-ring to prevent extrusion into the clearance gap at elevated pressure.

The material holds up against strong acids and bases, nearly all industrial chemicals, and solvents. That behavior comes from the compound itself: PTFE (Teflon) is specified for a very wide continuous service temperature range and near-universal chemical inertness. The material carries a published service range of -65°F (-53.9°C) to 500°F (260°C).

Maintenance and OEM teams specify it across chemical processing, aggressive-media pipelines, and pharmaceutical and biotech.

TST357 ships individually. Nominal inside diameter is listed as 5 1/2 inch. Check the compound against your process media, pressure and temperature before committing to a design.