Our HB24 measures 4"L x 2"W x 3/8" thick.  This extremely hard and fine unmounted stone is often used for the final finish on gravers and cutting tools. Can be used on both sides. Norton Arkansas Stones have gained a reputation over the years as the finest all-purpose stones for deburring and polishing operations as well as for sharpening precision tools. Hard Arkansas Stones are dense and fine-grained for final honing where the sharpest precision edges possible are needed. Not oil filled so should be used with Gesswein Stoning Oil for best results.