This is ReveD Aluminum 1mm Thickness Crab Spacer Set Black. The crab spacer, which has a crab claw-shape for ease of use enables you to adjust/remove by simply loosening the screws! You can easily change the settings to optimize the traction performance by adjusting the roll rigidity of the chassis according to the road surface condition you are driving! There are 2 versions, one for 【MC-1】 use and another for General use. The 【MC-1】 set consists of a set of spacers (dedicated 2-hole type and 1-hole type, total 6 pieces) perfect for adjusting the height of the gear case, altering driveshaft angles and upper mount positions.