I think it's quite a bit too wide. The RMD is a fair amount thinner than the Regulator....5/16 on the reg as opposed to 3/16 (I think) on the RMD. I think it would probably fit but it will rattle around quite a bit. Still though if you're looking to save cash I'm sure it could work, just wouldn't be perfect. I'll have my RMD tomorrow morning and I'll test it out for you.