Tillett Kart Seat Ultra Low Profile Washer (2.5mm thick)

The incredibly flat bolt and washer(2.5mm thick) combination does not destroy you race suit, your rib protector, or your body. They enable you to tighten the seat bolts without fear of the washer pulling through, as they often do with plastic countersunk washers, or bottoming out as they can do with regular aluminum washers. The design of the washer is such that it allows the head of the bolt to twist in the washer which stops the seat from breaking during the twisting forces generated by the chassis.