2103-339 PTFE S/T BUP FDA

TST339 is an AS568-339 white PTFE (Teflon) 55 Shore D Back-Up Ring built to an inside diameter of 3.225 in (81.92 mm), a cross section of 0.21 in (5.33 mm), and an outside diameter of 3.645 in (92.58 mm). In service, this back-up ring installs on the low-pressure side of an o-ring to prevent extrusion into the clearance gap at elevated pressure.

PTFE (Teflon) is valued for excellent dielectric properties and one of the lowest coefficients of friction of any solid. The compound resists strong acids and bases, nearly all industrial chemicals, and steam. Rated temperature range runs from -65°F (-53.9°C) to 500°F (260°C) in continuous service. Applications involving molten alkali metals or service requiring elastic recovery call for a different compound.

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

Order part number TST339, sold individually. Nominal inside diameter is listed as 3 1/4 inch. Application requirements vary, so validate compatibility with your process conditions prior to installation. APG supports cross-referencing from drawings, samples and competitor numbers when a listed size is not an exact fit.