2801 Series Zinc Plated Steel Washer (4mm ID x 8mm OD) - 25 Pack

These 4mm washers are compatible with M4 hardware, commonly used when mixing goBILDA parts in with the Actobotics build system. Flat washers act to increase the surface area under the head of the screw. While not typically necessary on metals, we do recommend adding a washer under the head of each screw when working with plastics.