Under the stock lock
ring unit is the picturesquely named drop-deviation plate, which performs both the familiar function of regulating drop and cast and also serving as the rear mounting point for the lower receiver.
A pistol grip stock locks
you into the set length-of-pull, which on the TEC 12 is 14-1/2 inches.
Once installed, the locks work more smoothly than the stock locks
did and, as noted, are more tamper-and pick-proof.
The side-folding triangular stock locks
solidly in place.
Avganim says to be sure to stock locks
with metal parts, not plastic.