390 PTFE SOLID BACKUP RING FDA

Use item TST390SO when a PTFE 90A Backup Ring is required for anti-extrusion support behind O-rings in high-pressure hydraulic and pneumatic glands. The item is specified by AS568-390; 20.953 inch (532.21 mm) ID x 0.21 inch (5.33 mm) CS; 21.373 inch (542.87 mm) OD, with 21 inch nominal ID; 3/16 inch nominal CS for cross-reference against common gland and replacement dimensions. The PTFE construction supports chemical resistance, low friction and low surface energy in demanding static sealing applications. It is with a listed temperature range of -65°F (-53.9°C) to 500°F (260°C), which can help narrow material selection for heat, cold or process exposure. The white color and round profile provide a practical visual identifier during receiving, stocking and installation. As a backup ring, it works with a primary O-ring to help limit extrusion into clearance gaps under pressure. The each-unit format supports precise replacement, kitting, resale and job-specific purchasing. Important product identifiers include O-rings, replacement seals, fluid sealing, material compatibility and dimensional fit. It supports customer comparison, distributor cataloging and specification-based selection without relying on pricing, availability or shipping claims.