Joint protectors are made to serve 3 main purposes: to reduce the risk of bending joint pin, to protect the joint collars from damage due to an impact, and to keep dirt and debris out of the joint. Joint protectors are an inexpensive way to help preserve your cue investment. These joint protectors are made from Cerocite, a high-impact plastic. Common cue brands featuring the 5/16 x 18 joint style are Dufferin Marble, 200, 300, Radical, Sabre Series, Nemesis, Meucci, Sterling, Action, Stealth, Viking, and Mali.