Tyler T-grips were made of aluminum--I guess by casting. They had a finger groove near the bottom, so they were described as "contour."

Mershon and Pachmayr were two other companies that made grip adapters. I believe their material was hard rubber or composition of some type. They had a bronze spring clip screwed to their back, with two prongs that slipped over the front strap, one on each side. The regular wooden stock screw clamped the adapter in place. These grips had no finger grooves; just a smooth curve to fill in the space behind the trigger guard, curving down to the bottom of the front strap.

These were made to fit different makes & models of revolver frame sizes. Also, there were different sizes on at least one, if not both brands, designated small, medium & large, based on the amount of depth behind the trigger guard. These sold for approx $2 during the 1950s. I don't know if Pachmayr still makes them; I think Mershon is no longer in business. Old issues of Stoeger "Shooters Bible" show The Pachmayrs.

I hope the above info may be helpful.