Every tube connection in a milking machine — where the milk tube meets the claw, where the vacuum hose meets the pulsator, and so on — relies on a secure, airtight seal to maintain proper vacuum pressure. The Pipe Clip is what holds those connections tight. It's a simple part, but a worn or missing clip is a surprisingly common cause of vacuum fluctuation, since even a small air gap at a connection point pulls vacuum away from where it's actually needed at the teat cups.
Because it's inexpensive and used in multiple places throughout the system, most farms are better off keeping a small stock of spare clips on hand rather than waiting until one fails and ordering a single replacement — a five-minute fix becomes a bigger problem if milking has to stop because you don't have one in the shed.