The Uni-Loc weight cartridge system has been used on P3 cues since 2008, and then used on all Predator cues introduced since 2008.
We have been sold out for some time of the spare weight bolts that were used on Predator cues before the current Uni-Loc weight cartridge system.
If you have a Predator cue that was made before the current Uni-Loc Weight Cartridge System and you need a replacement weight bolt. The thread size is 3/8x16 and the head style is flat. You can find it in a local hardware store.