Between each teat cup liner and the central claw sits a short section of tubing — much shorter than the 1-metre Milk Tube that carries milk onward from the claw to the bucket, but doing a related job at a smaller scale. Because there are four of these per cluster (one for each teat cup) and they flex constantly at both the liner end and the claw end throughout every milking session, they tend to wear and need replacement more frequently, relative to their size, than almost any other tubing in the system.
Selling this in a pack of 10 reflects how farms actually use it — with four needed per cluster and most dairy operations running two, three, or more clusters (per our 2-in-1, 3-in-1, and Double Bucket machines), having a stock of spares on hand means a torn or perished short tube during milking is a quick swap rather than a delay.