8-256 BLACK FKM 90D BACK-UP RING

Part number VBU90256 is an AS568-256 black Viton® (FKM) 90 Shore A Back-Up Ring built to an inside diameter of 5.734 in (145.64 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 6.012 in (152.7 mm). A back-up ring extends o-ring service life by supporting the seal against extrusion under high pressure.

Viton® (FKM) is specified here for excellent resistance to compression set and permeation, industry benchmark where nitrile reaches its thermal limit. Expect good resistance to many acids, aggressive chemicals, and aromatic hydrocarbons. Published continuous service range is -15°F (-26.1°C) to 400°F (204.4°C). It is not the right choice where ketones and esters or hot water and steam are present.

Maintenance and OEM teams specify it across chemical processing, high-temperature process equipment, and aerospace.

This item is sold individually under part number VBU90256. Review your operating media and conditions against this specification before installation. Not finding the exact configuration you need? APG cross-references from prints, samples and competitor part numbers.