Thes come on all of our pre-tied PA rigs and have duel purpose, once you have pulled your pellet/bait on the hair and used your chosen bait stop you pull these rubber stops down to the bait keeping it from riding up the hair and also it helps plug pellets to stop the water ingress.
 
This come in 3 sizes and will double up as float/ledger stops
Small 5mm width x 4mm length
Medium 4mm width x 7mm length
Large 5mm width x 8mm length