8-350 BLACK FKM 90D BACK-UP RING

APG stocks the VBU90350, an AS568-350 black Viton® (FKM) 90 Shore A Back-Up Ring with an inside diameter of 4.6 in (116.84 mm), a cross section of 0.21 in (5.33 mm), and an outside diameter of 5.02 in (127.51 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) delivers the industry benchmark where nitrile reaches its thermal limit and outstanding high-temperature capability. This material stands up to engine and transmission fluids, chlorinated solvents, and petroleum oils and fuels. Service temperature is rated from -15°F (-26.1°C) through 400°F (204.4°C). It is not the right choice where low-molecular-weight organic acids or ketones and esters are present.

Maintenance and OEM teams specify it across oil and gas, chemical processing, and automotive fuel systems.

VBU90350 ships individually. Unit weight is approximately 5.3897 g and nominal inside diameter is listed as 4 5/8 inch. Application requirements vary, so validate compatibility with your process conditions prior to installation. 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.