Ive got a vibe, and yes its a great marker for what it is. You turn it clockwise to increase velocity, but if you bought it new you shouldnt need to adjust it. I never have and its been cosistent at about 270 - 280 over the chrono, same again though if you bought it new you should have a manual in the pack... it usually hidden under the plastic tray. would recomend a freak Jr kit and on off airport for it though!