TP3921
The TP3921 is an adapter for the PRAM Front Tap Shoes (TP1047-100 PRAM, TP1087-100 PRAM, and TP1290-100 PRAM) which allows the double pins to be converted to single pins.
To install, remove head from existing Amp connector, place the TP3921 on the open male Bail Lock Amp, then connect the head back on (click on diagram below for explanation)