Nọmba ọkọlọtọ mba maka skru isi hexagon bụ GB70-1985. E nwere ọtụtụ nkọwa na nha, gụnyere 3 * 8, 3 * 10, 3 * 12, 3 * 16, 3 * 20, 3 * 25, 3 * 30, 3 * 45, 4 * 8, 4 * 10, 4 * 12, 4 * 16, 4 * 4 * 4 * 4 * 4 * 35, 4 * 45, 5 * 10, 5 * 12, 5 * 16, 5 * 20, 5 * 25, 6 * 12, 6 * 14, 6 * 16, 6 * 25, 8 * 14, 8 * 16, 8 * 20, 8 * 20, 8 * 40, na ihe ndị ọzọ.