Ordered as TST475, this is an AS568-475 white PTFE (Teflon) 55 Shore D Back-Up Ring measuring an inside diameter of 25.94 in (658.88 mm), a cross section of 0.275 in (6.99 mm), and an outside diameter of 26.49 in (672.85 mm). The back-up ring bridges the extrusion gap so the primary seal holds its shape under load.
The material holds up against steam, solvents, and strong acids and bases. That behavior comes from the compound itself: PTFE (Teflon) offers near-universal chemical inertness and excellent dielectric properties. The material carries a published service range of -65°F (-53.9°C) to 500°F (260°C). Exposure to molten alkali metals or elemental fluorine at temperature will shorten service life.
You will find this material specified across pharmaceutical and biotech, laboratory equipment, and aggressive-media pipelines.
TST475 ships individually. Nominal inside diameter is listed as 26 inch. As always, verify media compatibility and operating conditions against the requirements of your specific application. If you need a size, durometer or compound that is not listed, APG can cross-reference from a print, a sample or a competitor part number.
description 2103-475 PTFE S/T BUP FDA
Actual_CS 0.275 inch (6.99 mm)
Actual_ID 25.94 inch (658.88 mm)
Actual_OD 26.49 inch (672.85 mm)
ProductCode Description O-Rings - Backup Rings