These 13mm pool cue tips with aperture are attached to a threaded brass retainer which simply screws onto the CueSight laser unit. This is the replacement leather tip, laser lens, and brass housing that goes on the CueSight laser-guided cue. It simply threads on to the cue. Replacement is a breeze! Note that these are for use only with the CueSight Laser-Sighted Billiard Cue, and are not for use with any other stick. Wouldn't it be easier to go ahead and order an extra one now?