The TST208 is an AS568-208 white PTFE (Teflon) 55 Shore D Back-Up Ring measuring an inside diameter of 0.609 in (15.47 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 0.887 in (22.53 mm). This back-up ring extends o-ring service life by supporting the seal against extrusion under high pressure.
This material stands up to oxidizing media, strong acids and bases, and nearly all industrial chemicals. PTFE (Teflon) is widely chosen for excellent dielectric properties and one of the lowest coefficients of friction of any solid. Continuous operating temperature is published at -65°F (-53.9°C) to 500°F (260°C).
Maintenance and OEM teams specify it across semiconductor fabrication, pharmaceutical and biotech, and aggressive-media pipelines.
TST208 ships individually. Review your operating media and conditions against this specification before installation. APG supports cross-referencing from drawings, samples and competitor numbers when a listed size is not an exact fit.
Description 2103-208 PTFE S/T BUP FDA
Actual Cross Section 0.139 inch (3.53 mm)
Actual Inside Diameter 0.609 inch (15.47 mm)
Actual Outside Diameter 0.887 inch (22.53 mm)
Measurement System Imperial
Product Category O-Rings - Backup Rings