This is a 30mm ring mount is probably the best opition over the other two version that have been out there. When the discussion of a side mount that would co-witness was wanted, this was the one referenced in the first place. Apparently Tim finally got them to import it! It should co-witness with a lot of rifles and allows a little more mounting options with the rail. Looks like you could even use offset rings that are currently being used for flashlights.