Samix TRX-4 Brass Hex Adapters help add a bit more unsprung weight, and add 8mm of length to your track width. The hubs weigh 6.5 grams each (26g total), so they add minimal rotating weight to the drivetrain. They are easy to install using the stock hardware and will help to increase the overall stability of the model. Features: 8mm thickness Made of high quality CNC machined brass Direct fit standard TRX-4 Black finish with gold chamferred edges Width marked on the side for easy identification