The specs listed appear to be a mix of 20cc (weight) and 30cc (bore:stroke, props).....I'd call and check with Tom Denney. He is a good chap to deal with

I really appreciate what DLE has done with the prop mount. No reason to install props with the screwey screws for anything up to 100 cc. This little mill is one compact little jewel. I just might get one to play with myself