2pcs M4x20mm 10.9 Grade Flat Countersunk Head Hex Socket Left Hand Thread Bolt

Made of 40Cr Steel material black oxide finish hex socket flat head left hand reverse thread design. Fixing component industrial and construction fasteners. To tighten a reverse threaded screw you turn it counter clockwise.To loosen a reverse threaded screw you turn it clockwise. Used widely in home office and factory appliance communication equipments ship assembly and other machinery industry.