15076 Size: No.1 Features: -Recess power bit.-Precision-ground spur and cutting edges for smoother, faster cuts.-Manufactured from special shock-resistant alloy steel.-Fully hardened and tempered to all-hard status.-Tough enough to drive sheet metal and case-hardened screws.-0.25" Hex shank with power groove fits all power screwdrivers and variable speed drills. Dimensions: -No.1 Dimensions: 1" H x 1.5" W x 1.9" D.-No.3 Dimensions: 7.4" H x 1.2" W x 1.9" D.