3/4"-1" (19.1-25.4mm) diameter.
Carbide Drills are recommended for cleaning straight ferrous tubes plugged solidly with deposit.
Note: GTC-229 can be attached to GTC-227 Flex Hub and GTC-231D can be attached to GTC-231 Flex Hub.
Note: All drills run 10% oversize [e.g. GTC-231D Drill is 0.825" (21.0mm) O.D.].