Hi Sean. It's a shame you don't have a 22.5 WSM as you would then be able to buy a Cajun Bandit rotisserie ring. It is reversible and would allow you to use your rotisserie on both. Since you have a 18 WSM, I would recommend that you buy a ring for your 22 OTP as I think you would have more versatility by using it on your grill. I would also recommend that you buy the reversible ring offered by Cajun Bandit. It is designed to fit snugly over the edge of your kettle as opposed to the much looser fit offered by the ring offered by Weber. I have both and rarely, if ever use the Weber ring anymore.