Infly Fasteners is a factory and manufacturers of fasteners and bolt in china, there are square nuts in stock sales any time, all square nut are self colour, if you need zinc or other surface, please let's know.
About DIN557 square nuts, the size in stock as following:
Size: M12, M16, M20, 3/8", 1/2", 5/8", 3/4"
Material: Class 4.8, Carbon steel Q195
Surface: Self colour, White Zinc, Blue Zinc, H.D.G.
Packing: Carton bulk 20KG-25KG and then on pallet.
Contact: Mr.Lufel Lee
Add: No.333 Xinqiao Road, Haiyan, Jiaxing City, ZJ China.