20 Sizes of Round Holes: Our forming block offers a comprehensive range of round hole sizes, catering to various jewelry making needs. Sizes include: 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, and 20mm.