8-346 BLACK FKM 90D BACK-UP RING

VBU90346 is an AS568-346 black Viton® (FKM) 90 Shore A Back-Up Ring supplied with an inside diameter of 4.1 in (104.14 mm), a cross section of 0.21 in (5.33 mm), and an outside diameter of 4.52 in (114.81 mm). In service, this 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) offers the industry benchmark where nitrile reaches its thermal limit and very low compression set at elevated temperature. The compound resists aromatic hydrocarbons, many acids, and aggressive chemicals. Rated temperature range runs from -15°F (-26.1°C) to 400°F (204.4°C) in continuous service. Verify compatibility before use with amines or ketones and esters.

Maintenance and OEM teams specify it across automotive fuel systems, high-temperature process equipment, and aerospace.

Reference part number VBU90346 when ordering; the item is sold individually. Unit weight is approximately 4.7927 g and nominal inside diameter is listed as 4 1/8 inch. Review your operating media and conditions against this specification before 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.