This pack of 12 Official Fender Stratocaster Tremolo Arm Tension Springs are used to stop the tremolo arm hanging loose and to keep it in the desired playing position. Simply place a spring in the tremolo arm hole in the bridge and then screw the arm in until it reaches the spring, the spring will keep the arm in place when not in use to stop it flopping around. The springs fit American Vintage, American Standard, Classic, Deluxe and Road Worn series Stratocaster models.