O-ring, 28 x 1.5mm – Viton, Part# 320276

The material. It is made from Viton, which is a type of FKM rubber . Regular rubber gets hard and cracks when it gets hot. It can also swell up when it touches oil.

Viton does the opposite. It stays soft and flexible. It handles the heat without breaking down. And it stands up to oils and chemicals very well . That makes it perfect for vacuum pumps that work hard every day.This O-ring has a hardness rating of about 75 Shore A . Think of it like this: too hard and the ring won’t squish enough to seal. Too soft and it might pinch or tear. 75 Shore A is the “sweet spot.” It seals tight, but it also lasts a long time.

This specific O-ring is used in many popular Busch pump models. You will find it inside the Busch MD, ME, MV, and MZ series . Here are the exact models it fits:

• MD Series: MD4, MD4T, MD8

• ME Series: ME8, ME16

• MV Series: MV2

• MZ Series: MZ4, MZ8, MZ2D 

This O-ring is also included in factory seal kits. For example, it comes with the Vacuubrand MV2 seal kit (Part# VSK011) and MZ2D seal kit (Part# VSK012) .