[head type], 1. Flat head, 2. Countersunk head, 3. Small countersunk head, [column type], 1. Park rod type, 2. Groove, 3. Hexagonal (semi-hexagonal), [stainless steel small countersunk head insert nuts column type], carbon steel, aluminum, stainless steelb rass, etc., [product specifications], 1. M3, m4, m m5, m6, m8, m10, m12, 2. 6-32, 8-32, 10-32, 1/4-20, 5/16-18, 3/8-16, 1/2-13, ,
