Uses a tiny set screw to lock er' down. Can use some blue 242 on the allen screw. If you order a barrel from Javis, and plan on using a lone Wolf compensator, you can ask Jarvis to mill a little flat spot on the bottom of the barrel, corresponding to the location of the allen/set screw. I sent em' my compensator so they could fit/measure to get the milling correct. If they kept notes they could just refer back to what they did on mine.....if not, you might want to send your compensator to em'.