O-ring, 180 x 5 mm – Viton, Part# 320534

This is a large Viton O-ring. Its part number is 320534. An O-ring is a simple loop of elastic material. Its shape is a perfect circle. When you look at a cross-section, it looks like the letter “O”. That is where the name comes from.

You place this O-ring into a groove between two large metal parts. When you tighten the parts together, the O-ring gets squished. It fills the tiny gap completely. This creates an airtight, leak-proof seal .

This O-ring is made specifically for one pump model:

• Pfeiffer DUO 255M (Index C) 

The DUO 255M is a special version of the DUO 255. It uses a magnetic coupling instead of a traditional shaft seal. This design avoids oil leaks at the shaft. If you own this pump and are doing any internal repair or rebuild, you will need this O-ring.