One of the simplest and best creations ever. Back in the early '80s when Colt reintroduced the Agent, a .38 Special six shot revolver, the grip panels were too small for a good grip. I tried various aftermarket grips but most caused printing when I carried the Agent. (Different state and I had a permit) Someone somewhere suggested the T-Grip and I got one. I put the factory grip panels back on, with the adapter and the gun was then comfortable to carry and shot like a dream.
Be careful with the trigger shoes if you use a holster. Some of them can be wider than the trigger guard.
At work they used to have Range Revolver with square bottom Magnas. , and a grip adapter as an orthopedic gun for small handed people. If no actual munchkins needed it , I would use it because I have less than ideal fit to the issued grips.
Bottom line : with the grip adapter gave indexing as good as nice fitting boot grips, but the control ( torquing in hand) not as good. *For me* an acceptble trade off up thru .38+P .