Spacer, UNO/DUO250, Pfeiffer, DUO, UNO, Part# 440055 – vacstellar

This is a spacer designed for Pfeiffer DUO 250A, DUO 255M, and UNO 250A vacuum pumps. It maintains proper clearances between internal components, ensuring correct alignment and reliable operation . This spacer is used in larger Pfeiffer pump models. It fits the DUO 250A, DUO 255M (Index C), and UNO 250A pumps . These are industrial‑grade pumps that run in demanding applications.

You will often find this spacer included in major overhaul kits. For example, it is part of the PMK026 Overhaul Kit for the UNO 250A pump . It is also included in the PSK027 Seal Kit for the DUO 250A pump . That means it is a standard part that gets replaced during a full pump rebuild.

If you are already opening up your pump for service, replacing this spacer is a smart move. A fresh spacer ensures correct clearances and helps your pump run like new.