I love them in guns that will use them. Some guns don't like the buffers because they shorten the slide stroke making lockback or slingshot style slide release difficult or impossible.
Test your gun with the buffer in place by inserting an empty mag and racking the slide. If it will lock back you have won half the battle. Some of mine will lock but not release by pulling the slide so I just thumb the slide stop.
Find out from your friend which brand/thickness shok buff he bought. On one of my guns I have to use the Hiett Red Buffs in .090 thickness. They work so well I just buy the thin ones these days.
Mikey