Rubber Stops are used to control the distance between the sinker, the hook, and the lure without having to redo the entire rig. The soft rubber conforms to the nylon or fluorocarbon line and helps protect the knots from repeated impacts by the sinker. On a Carolina rig, they keep the sinker at the desired distance while maintaining a clean presentation. On a Texas rig or with a sliding sinker, they prevent the sinker from drifting too far during retrieves. The choice between M and L depends on the line diameter used and the desired hold.