The TST438 is an AS568-438 white PTFE (Teflon) 55 Shore D Back-Up Ring measuring an inside diameter of 6.225 in (158.12 mm), a cross section of 0.275 in (6.99 mm), and an outside diameter of 6.775 in (172.09 mm). This back-up ring allows a standard o-ring to operate at higher pressures than it could unsupported.
It resists strong acids and bases, oxidizing media, and steam. That behavior comes from the compound itself: PTFE (Teflon) is specified for near-universal chemical inertness and non-stick, non-contaminating surface characteristics. The material carries a published service range of -65°F (-53.9°C) to 500°F (260°C).
Typical settings include chemical processing, aggressive-media pipelines, and pharmaceutical and biotech.
Order part number TST438, sold individually. Nominal inside diameter is listed as 6 1/4 inch. Application requirements vary, so validate compatibility with your process conditions prior to installation.
Description *2103-438 PTFE S/T BUP FDA
Actual Cross Section 0.275 inch (6.99 mm)
Actual Inside Diameter 6.225 inch (158.12 mm)
Actual Outside Diameter 6.775 inch (172.09 mm)
Measurement System Imperial
Product Category O-Rings - Backup Rings