Nozzle for de m4

I'm trying to make my de m4 the best it can be. I'm adding 13:1 gears but the nozzle sits still an issue. Form what I can tell it's a 21.2-21.3. nom not using a Maxx because I've had 2 guns with a max nozzle that gave me no air seal because I want using a Maxx cylinder head th edits one was whee I tried it in my cyma paltunum mp5. It takes m4 nozzles because that's the nozzle I have in it. The other one uses a gate cylinder head as it's a dmr. I also prefer single o rings as they have some give to help with mid cap syndrome should it arise. So can I get a reccomendation since they didn't always tell you anything about the nozzle.you're buying