Hollow and solid handles have an improved design that features enhanced tactile grip knurlings. Hollow: 8-mm diameter and 20 g; Solid: 6.5-mm diameter and 27-g DH #2 Octagonal handles were designed by Dr. Stan Hoovers. They are lightweight hollow handles with space for color rings for easy identification. 6.5-mm diameter and 21-g Gracey Longs are designed for pockets deeper than 5 mm.