I am in no way affiliated with Cobra's Custom, but I have to say, the Winchoke adapter they sell is absolutely, hands down, the best part I have put on my beloved Saiga 12. They are extremely well made, look awesome, and pattern great. Beats the hell out of the Polychoke by a mile!
If you don't have one, and are thinking about putting a choke on your shotgun so you can blast skeet with a 20 round drum, making all those fancy, pretty shotgun owners jealous...definitely get your hands on one, you won't be disappointed.