8-349 BLACK FKM 90D BACK-UP RING

APG stocks the VBU90349, an AS568-349 black Viton® (FKM) 90 Shore A Back-Up Ring built to an inside diameter of 4.475 in (113.67 mm), a cross section of 0.21 in (5.33 mm), and an outside diameter of 4.895 in (124.33 mm). A back-up ring allows a standard o-ring to operate at higher pressures than it could unsupported.

Viton® (FKM) is known for very low compression set at elevated temperature and the industry benchmark where nitrile reaches its thermal limit. The material holds up against aromatic hydrocarbons, chlorinated solvents, and engine and transmission fluids. Service temperature is rated from -15°F (-26.1°C) through 400°F (204.4°C).

Typical settings include aerospace, oil and gas, and chemical processing.

Reference part number VBU90349 when ordering; the item is sold individually. Unit weight is approximately 5.2996 g and nominal inside diameter is listed as 4 1/2 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.