438 PTFE SOLID BACKUP RING FDA

Item TST438SO is a PTFE 55D Backup Ring built for anti-extrusion support behind O-rings in high-pressure hydraulic and pneumatic glands. The item is specified by AS568-438; 6.225 inch (158.12 mm) ID x 0.275 inch (6.99 mm) CS; 6.775 inch (172.09 mm) OD, with 6 1/4 inch nominal ID; 1/4 inch nominal CS for cross-reference against common gland and replacement dimensions. The PTFE compound is selected for 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. Key selection details include material, hardness, product type, cross-section, inside diameter, outside diameter and application. These specification details help customers and resellers compare the part by performance requirements rather than brand name alone.