QLT By MARSHALLTOWN 7554 1/2-Inch Depth, 3/8-Inch Width, 1/4-Inch Radius Bronze Fresno Groover Attachment Made from high quality, long wearing bronze alloy Finely finished to make smooth, clean edges Two thumbscrews are used to tighten the attachment to the fresno Designed to slip easily over a fresno trowel Radius is 1/4-Inch