The Yamaha RMX II is a yamaha vibrato system used in some 80's and 90's Yamaha guitars. The Yamaha catalog says the following. " The RMX II vibrato system gives you smooth, free up and down bending, and locks the string firmly at the nut to maintain perfect tuning. The arm conveniently snaps in and out, and the tailpiece has fine tuners for fingertip adjustment. The tremolo is available in black or chrome.