Its a h22 block lol thats all im at liberty to say. It might be a tad bigger then a h22 just a tad lol. My dad hates claying so one day he grabs a old head that i had laying in the junk pile and turns the blade backwards in the skill saw, well you see the results lol. If you dont mine save me a old b16 and b18 head (i dont get many at my shop )thats toast if you have one and ill make both of us one of these ,it sure makes things easy.