Thank you for viewing. This is a set of 4 discharge washers. While they can be used with M8 bolts, they are typically used on wheel air valves. To enhance the synergistic effect, Ice Fuse's Fast Liquid (antistatic agent) has been applied. These washers allow for the air discharge of static electricity from the vehicle body, and are also expected to be effective in removing static electricity generated by tire friction, leading to: Changes in tire grip Improved fuel efficiency, etc. They can be used in various locations on the vehicle, so why not try them in places other than the air valves? This is a set of 4, enough for one car. Instant purchase is welcome.