Made of low carbon steel, zinc plated The nut is a thinwall half hex insert for use in hexagon holes. Designed for use with spin-spin or spin-pull tools The low profile head is wide and thin and allows for a near flush installation. Swordfish 30420 - American Standard Metric and SAE Hex Type Thin Sheet Nut-Insert Nutserts Rivnut Rivet Nut Assortment, Size from #6 to 3/8" and M4 to M10, total 12 sizes, package of 190 pieces