Suki M5 Domed Cap Hex Nuts are six-sided nuts with a dome shape and with nylon-filled collars These collars adhere to the thread of the fastener bolt or screw giving a more secure fix When a bolt or screw reaches the collar, the threads and nylon form a tight, frictional fit, restricting movement of the fastener It also conforms to the product standards of DIN 986 It is resistant to corrosion