Countersunk head blue nylok machine screw; Stainess steel, etc. Anti-loose nylok; Used on machinery etc ... RoHS compliant. Phiilips Countersunk head nylok screw:Item name: nylok screw; Material: stainless steel,iron,carbon steel,aluminum,brass ... with nylok;Head Type: pan head,truss head,bind head,flat head,oval head,round head,etc.Standard: JIS,BS,GB ...