The washer is a thin disk-shaped plate with a hole in the middle that is normally used to distribute the load of a threaded fastener, such as a screw or nut. Other uses are as a spacer, wear pad, pre-load indicating device, locking device, and to reduce vibration. High-quality bolted joints require washers to prevent the loss of pre-load after the torque is applied. Washers are also important for preventing galvanic corrosion, particularly by insulating steel screws from aluminum surfaces. Features: This set of flat washers are made of high quality copper of good electrical conductivity and thermal conductivity. Flat washers can spread a load, and prevent damage to the surface being fixed, and insulate steel screws from surface. Can be used as a spacer, wear pad, pre-load indicating device, locking device, and to reduce vibration. Flat washer is applied when the hole is a larger diameter than the fixing nut. There are many different sizes of washers in this set from which you can use for different purposes. This set includes many flat washers that can be used for a long time, so you don't have to run to hardware store looking for washers for quite a while. Specifications: Material: Copper Type: Flat washer ID*OD*Thickness(mm) & Quantity: M5*9*1 30pcs M6*10*1 30pcs M6*12*1 20pcs M8*12*1 20pcs M8*14*1 20pcs M10*14*1 20pcs M12*16*1 20pcs M12*18*1.5 20pcs M14*18*1 20pcs Box Size: 130 x 68 x 22mm / 5.12 x 2.67 x 0.86" Package Includes: 200pcs x Washers