The TST106 is an AS568-106 white PTFE (Teflon) 55 Shore D Back-Up Ring supplied with an inside diameter of 0.174 in (4.42 mm), a cross section of 0.103 in (2.62 mm), and an outside diameter of 0.38 in (9.65 mm). This back-up ring installs on the low-pressure side of an o-ring to prevent extrusion into the clearance gap at elevated pressure.
It resists solvents, steam, and oxidizing media. That behavior comes from the compound itself: PTFE (Teflon) is widely chosen for near-universal chemical inertness and one of the lowest coefficients of friction of any solid. The material carries a published service range of -65°F (-53.9°C) to 500°F (260°C).
Common environments for this compound include food and beverage, aggressive-media pipelines, and pharmaceutical and biotech.
Stocked as TST106 and sold individually. Nominal inside diameter is listed as 3/16 inch. Review your operating media and conditions against this specification before installation.
Description 2103-106 PTFE S/T BUP FDA
Actual Cross Section 0.103 inch (2.62 mm)
Actual Inside Diameter 0.174 inch (4.42 mm)
Actual Outside Diameter 0.38 inch (9.65 mm)
Measurement System Imperial
Product Category O-Rings - Backup Rings