These screws fully comply with **GB839 standard** and are made of high-quality **35K steel**, with excellent strength and toughness to meet long-term industrial use. Adopting slotted drive, high knurled head and captive non-falling design, the knurled surface allows easy hand tightening without tools, while the captive structure effectively prevents the screw from disengaging from the workpiece. With precise machining and stable fitting performance, they are widely used in electrical cabinets, instrument panels, mechanical covers and equipment that requires frequent disassembly and anti-loss fastening. Each piece is strictly inspected for dimensional accuracy and quality; factory direct supply with complete specifications, providing reliable hand-operated anti-lost fastening solutions.