5/16 x 18 thread standard joint protectors.
Joint protectors will protect the only moving part on your cue... The Joint. Joint Protectors protect the pin of the cue butt from any accidental side pressure blows, keeping your cue pin straight and true so preserve the accuracy and straightness of your pool cue investment.
The cue shaft protector keeps the joint end of the cue shaft from accumulating dirt, sand, and other debris that, when left unprotected, can gather in the pocket of the joint in the cue shaft. This debris can cause damage when the pin is screwed into the shaft.
Sand and dirt can cause the pin and joint to grind and bind while screwing on your shaft, possibly locking the two together. Protect your most important billiard equipment, your pool cue with a set of Quality Joint Protectors.