I bought the Adams Arms piston upper from midwayusa.com on sale now for around $550 and you can get a $50 discount if your on their email list. I've shot thousands of rounds including Wolf with zero issues. The bolt and carrier do stay cleaner and cooler. You will have to clean the piston every once in a while and wipe off the front of your hand guard if you wish. It all comes down to what you want. I wanted it, so I bought it, and like it. Sure it might not be absolutely necessary, but that's what we fought and fight for is your freedom of choice.