Four rivets hold the Velcro in place while the mops can be changed thousands of times before needing to be replaced. The mop head frame can be locked into place for a constant position or unlock the simple locking device to allow the mop head frame to swivel at a 360 degree angle. Frame Fits - Flat Mop (M830013) Blue, Green, Red / Scrub Mop (M80013) Blue, Green, Red.