The 2mm coated aluminum spacer fits under the differential and slots/keys toward framework. You are able to spot 2 alongside eachother to create 4mm spacer. The style is manufactured such method your 2 spacers will freeze spot. According to the meals utilize you may want to furthermore spot from the back stiffener. Increasing the rollcenter goes the differential greater aswell, creating more grip and steering, but less very easy to drive.