"The price on this nozzle is a bit obsurd(You can get a low end real Steel M16/AR15 bolt for the price of this), but if you're serious about your M4/M16 GBBR it's worth it. I am using this in my WE M16A3 currently and it has worked perfectly, and it is great being able to change the FPS for CQB, or max out the FPS to use it as a DMR. The adjustability of the FPS makes it possible to play almost any role with the same gun.
For some odd reason shortly after installing this my gun's auto sear started acting up and it would only work on semi, but I don't think it was anything to do with this part, it will work if you don't turn the switch all the way to auto though. Most GBBRs aren't suited to full auto fire too well anyways so it isn't a big issue, but I'm having it checked out soon.
Overall this is a great product and works perfectly, and should last forever unless abused, and is actually a good investment if you use your GBBR a lot, considering that the $20 plastic nozzles break about every 1000 rounds. Minus one start solely for the absurd price, but it's a 5/5 on performance."