I have an M95 in my M4 (CQB innit).
So far it's had SHS helical gears (which came out again when I realised I am NOT a shimming ninja), SHS piston head, SHS nozzle, Kanzen 6mm bearings and will soon have the aforementioned delayer chip and a Lonex 14 tooth piston (the one with the second tooth already removed) plus (if it ever gets here) an Airlab sorbo pad to sort out the AoE and stuffs.
It all started because it was shooting at around 220FPS and getting about 15m range regardless of the hop setup. The gun was cheap second hand and is no longer my primary (that honour goes to a G&G SCAR-L) so I decided to use it to learn how it all works (or more often doesn't). It's been educational. And expensive.