These are the black rubber washers that are attached to DragonFly Modular Ends to provide a tight fit when attaching the ends to a DragonFly shaft - which can become damaged or lost with use.

This replacement washer pack contains 8 washers - 2 small, 4 medium, and 2 large. Multiple sizes are used to compensate for the slight variation in weld size (the most common configuration used is 2 mediums per end, or 1 medium/1 small).