Busch O-Ring, 202.79 x 3.53 mm – Viton Part# 320271

This O-ring has an inner diameter of 202.79 mm and a cross-section (thickness) of 3.53 mm .

The inner diameter is about 8 inches. That is large. This O-ring is designed for big pump housings or large flange connections.This size is known in the industry as AS568 size 266 . This is a standard sizing system for O-rings. If you hear someone say “a 266 O-ring,” this is the one they mean.

Viton is a brand name for a type of synthetic rubber. The technical name is FKM (Fluoroelastomer) . Viton is special because it can handle things that destroy regular rubber:

• High temperatures – Works from -20°C up to +205°C 

• Harsh chemicals – Oils, fuels, aliphatic and aromatic hydrocarbons, and some fire-resistant oils 

• Vacuum pressure – Very low gas permeability makes it well suited for vacuum applications 

Standard rubber O-rings can swell, crack, or melt in these conditions. Viton keeps working.