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.