The TST345SO is an AS568-345 white PTFE (Teflon) 55 Shore D Back-Up Ring with an inside diameter of 3.975 in (100.97 mm), a cross section of 0.21 in (5.33 mm), and an outside diameter of 4.395 in (111.63 mm). This back-up ring extends o-ring service life by supporting the seal against extrusion under high pressure.
PTFE (Teflon) is specified here for very wide continuous service temperature range and non-stick, non-contaminating surface characteristics. This material stands up to oxidizing media, nearly all industrial chemicals, and solvents. Rated temperature range runs from -65°F (-53.9°C) to 500°F (260°C) in continuous service.
Maintenance and OEM teams specify it across chemical processing, pharmaceutical and biotech, and food and beverage.
TST345SO ships individually. Nominal inside diameter is listed as 4 inch. Check the compound against your process media, pressure and temperature before committing to a design. APG supports cross-referencing from drawings, samples and competitor numbers when a listed size is not an exact fit.
Description 345 PTFE SOLID BACKUP RING FDA
Actual Cross Section 0.21 inch (5.33 mm)
Actual Inside Diameter 3.975 inch (100.97 mm)
Actual Outside Diameter 4.395 inch (111.63 mm)
Measurement System Imperial
Product Category O-Rings - Backup Rings