Our Flat Dapping Block is made of alloy steel, hardened and polished. The smaller has 14 hemispheres : 25, 22, 20, 19, 17, 16, 14, 13, 11, 9, 7.5, 5.5, 4.5 and 3mm. The larger has 27 hemispheres : 1.5, 2, 2.4, 2.8, 3.2, 3.6, 4.4, 4.8, 5.6, 6.4, 7.1, 7.9, 8.7, 9.5, 10.7, 11.1, 12.7, 14.3, 15.5, 15.9, 17.1, 17.5, 19.1, 20.6, 22.2, 23.8 and 25.4mm