The Allparts Tremol-No is a patented device that is added to an electric guitar equipped with a tremolo/vibrato unit. It allows guitarists 3 playing options:1) tremolo unit "on" in this position your tremolo functions as normal. You can raise or lower the pitch of notes with the tremolo unit.2) tremolo unit "off" in this position, you"ll enjoy the benefits of a hardtail bridge, where the tremolo unit doesn"t move at all; no lowering or raising of a note"s pitch via the tremolo system, and the other strings remain in tune should you break one of them.3) tremolo unit "dive only mode" in this position, you can only lower the pitch of notes. If you break a string or drop tune the low E to D, the other strings will stay in tune.The Tremol-No comes in three versions: Pin-type (our sku# H71947), Clamp-type-large, (our sku# H71957), and Clamp-type-small (our sku# H71941). Please see the "Tremol-no works with chart" document attached for details on choosing the right one for your tremolo.Includes all hardware necessary.