LuKaiSen 631PCS M3 Hex Socket Head Cap Screws and Nuts Assortment Kit, Grade 12.9 Alloy Steel Metric Machine Bolts (M3 x 6/8/10/12/16/20mm) with Flat Washers & Wrench,Black Zinc Plated for 3D Printing

1. GRADE 12.9 ULTRA HIGH TENSILE STRENGTH: Crafted from premium alloy steel, our M3 screws meet the 12.9 grade industrial standard, providing superior tensile strength and hardness compared to stainless steel or 8.8 grade bolts. They are engineered for high-stress applications where durability and reliability are non-negotiable. 2. ADVANCED BLACK ZINC PLATED FINISH: Unlike common black oxide fasteners that may rub off or rust quickly, these screws feature a specialized Black Zinc Coating. This finish offers excellent corrosion resistance and a sleek, uniform black look, making them perfect for visible assemblies like PC builds and drone frames. 3. ESSENTIAL 631-PIECE METRIC SET: This comprehensive assortment includes 210 screws in 6 frequently used lengths (6mm, 8mm, 10mm, 12mm, 16mm, 20mm), plus 210 matching hex nuts and 210 flat washers. To ensure immediate use, we’ve also included a precision Allen wrench in every box. 4. PRECISION HEX SOCKET DRIVE: Designed with deep, standardized internal hex sockets, these cap screws provide a high-torque connection that resists stripping. The clean, burr-free threads ensure smooth engagement and a professional fastening experience for delicate electronics and heavy-duty machinery alike. 5. LABELED STORAGE FOR QUICK ACCESS: All 631 pieces are organized in a heavy-duty, transparent storage case with secure snap-locks. A detailed size chart is printed on the lid, allowing you to identify the exact length you need in seconds, keeping your workspace organized and efficient.