Keppeler makes a fine insert. I have had several drillings with Keppeler inserts and all worked superbly. They were all very accurate, always returned to zero after re-installation, and were easy to adjust. I am currently putting together a couple of Merkel 9.3x74R drillings with 9.3x74R Keppeler inserts in the left shotgun barrel. This is a good setup because the Merkel based actions are strong enough for a large bore insert. Not all drilling actions are.