390 PTFE SOLID BACKUP RING FDA

APG stocks the TST390SO, an AS568-390 white PTFE (Teflon) 90 Shore A Back-Up Ring with an inside diameter of 20.953 in (532.21 mm), a cross section of 0.21 in (5.33 mm), and an outside diameter of 21.373 in (542.87 mm). A back-up ring installs on the low-pressure side of an o-ring to prevent extrusion into the clearance gap at elevated pressure.

The material holds up against steam, oxidizing media, and solvents. PTFE (Teflon) is widely chosen for excellent dielectric properties and one of the lowest coefficients of friction of any solid. Service temperature is rated from -65°F (-53.9°C) through 500°F (260°C). It should not be specified for service in service requiring elastic recovery or elemental fluorine at temperature.

Maintenance and OEM teams specify it across semiconductor fabrication, food and beverage, and pharmaceutical and biotech.

Order part number TST390SO, sold individually. Nominal inside diameter is listed as 21 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.