**129 PTFE SOLID BACKUP RING FDA

Ordered as TST129SO, this is an AS568-129 white PTFE (Teflon) 55 Shore D Back-Up Ring with an inside diameter of 1.549 in (39.34 mm), a cross section of 0.103 in (2.62 mm), and an outside diameter of 1.755 in (44.58 mm). The back-up ring extends o-ring service life by supporting the seal against extrusion under high pressure.

It resists nearly all industrial chemicals, strong acids and bases, and steam. That behavior comes from the compound itself: PTFE (Teflon) is specified for non-stick, non-contaminating surface characteristics and one of the lowest coefficients of friction of any solid. The material carries a published service range of -65°F (-53.9°C) to 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 chemical processing, food and beverage, and pharmaceutical and biotech.

This item is sold individually under part number TST129SO. Nominal inside diameter is listed as 1 9/16 inch. Confirm chemical compatibility, pressure and temperature against your own application requirements before installing. For a size or compound outside the standard catalog, APG can quote from a print or sample.