330 Pcs Flat Copper Sealing Washers

This kit provides 330 individually counted flat copper washers across 12 standard metric sizes: M5, M6, M8, M10, M12, M14, M16 and M20. Quantities per size are balanced to reflect real-world usage frequency — larger sizes (e.g., M16, M20) are included in lower counts, while common sizes like M8 and M10 appear in higher volumes. All washers are made from commercially pure copper (Cu ≥ 99.7%), offering excellent malleability and natural resistance to atmospheric corrosion, oils and mild solvents. Typical thickness is 1.5 mm; outer diameters range from ~12 mm (M5) to ~32 mm (M20), with inner diameters sized to fit respective bolt threads with minimal clearance. Designed for single-use crush sealing, these washers deform plastically when tightened, filling microscopic surface irregularities between mating parts to form a gas- and liquid-tight barrier. Their performance is especially valuable where elastomer seals would swell, harden or extrude — such as high-temperature engine oil drains, diesel fuel lines or pressurised hydraulic ports. Copper’s non-magnetic and non-sparking properties also make them suitable for hazardous area maintenance. The kit supports scheduled maintenance across passenger cars, light commercial vehicles, agricultural machinery and stationary industrial equipment. It is frequently used by independent garages and fleet technicians for oil changes, transmission servicing, coolant system repairs and fuel system diagnostics. The transparent, stackable plastic case features embossed size labels and secure snap-fit dividers — keeping washers separated, dust-free and easily restocked after use.