The string tension is balanced against two medium length helical springs under tension, mounted on the underside of the tremolo mounting plate, one attached to each of the two feet of the tailpiece bar. Dynamic Vibrato units may be recognized by the integrated floating bridge and the stamps "Fender" and "DYNAMIC VIBRATO". Many but not all units also have the words "PAT PEND" or "PAT. NO. 3,241,418" stamped under the word "Fender". The Dynamic Vibrato was the last of the floating bridge designs Fender discontinued, with the Mustang in 1982—and the first they reintroduced, again with the Mustang, in 1990.