8-425 BLACK FKM 90D BACK-UP RING

APG stocks the VBU90425, an AS568-425 black Viton® (FKM) 90 Shore A Back-Up Ring supplied with an inside diameter of 4.475 in (113.67 mm), a cross section of 0.275 in (6.99 mm), and an outside diameter of 5.025 in (127.64 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.

As a material, Viton® (FKM) is valued for excellent resistance to compression set and permeation, the industry benchmark where nitrile reaches its thermal limit. The material holds up against engine and transmission fluids, chlorinated solvents, and aromatic hydrocarbons. Continuous operating temperature is published at -15°F (-26.1°C) to 400°F (204.4°C). It should not be specified for service in amines or low-molecular-weight organic acids.

You will find this material specified across chemical processing, aerospace, and automotive fuel systems.

Reference part number VBU90425 when ordering; the item is sold individually. Unit weight is approximately 10.932 g. Check the compound against your process media, pressure and temperature before committing to a design. If you need a size, durometer or compound that is not listed, APG can cross-reference from a print, a sample or a competitor part number.