UNC Hexagon full nut 1/4 inch -20 A4 Stainless Steel A4 grade stainless steel has a greater corrosion resistance than A2 in certain environments. It is often used for Marine applications especially when coming into direct contact with salt water Dimensions: 1/4" x 20 TPI 12 mm Across the flats 11 mm Point to Point 5 mm thickness