Phillips Button Head SEMS screw is pre-assembled unit: button head machine screw + flat washer + spring lock washer. The washers are fixed and cannot fall off.

Rounded curved head avoids scratches on cables and operators. Flat washer distributes pressure; spring washer provides anti-loosening elasticity. Materials: Grade 4.8 carbon steel; A2(304)/A4(316) stainless steel optional. Surface finish: blue-white zinc, yellow zinc, black oxide, stainless steel passivated finish. Widely used for electrical cabinets, elevator parts, sheet metal and decorative hardware assembly.