Here's the perfect solution for mounting your bottle stopper blank onto your PSI Bottle Stopper Chuck. With this system you just drill a blank then tap the thread that will mount your blank securely onto the chuck. Get a better grip with no more hand threading or spinning blanks! The set includes a 5/16" drill bit, a ratcheting reversible handle, and a centering tap to thread a 3/8" thread into your blank. Works great on wood, acrylic or any other machineable material.