They tighten up the cylinder slop, they also look good. They can help and also hurt group size, depends on the gun. They can be had with a set screw so the pin don’t flay out with heavy loads, some times if you torque the set screw to tight it will bind up the cylinder. They also have the Bowen stile and it should be installed by a good smith. I have them in most of mine and like them.