There are a lot of good chokes out there in 20g. I recommend a site call allaboutshooting.com the guy that runs this is a former world champ and sells chokes and such. I have the SSX by truglo on my 12g. contact him and he can give you a good idea what you might need. I would also look for deals on the undertaker, primo jelly head to name a couple that work. The best way to do it is by trial and error but that gets expensive LOL!