The GKTECH solid aluminium diff bushings are a direct replacement of the standard items and ensure that movement of the diff is kept to a minimum within the subframe which is quite common under hard driving conditions. In addition to limiting the movement of your rear diff our risers raise the diff within the subframe 20mm limiting the angle of your axles on a lowered vehicle. If your car isn't super low, the OEM style solid bush is suggested. - CNC machined 6061-T6 aluminium and anodized black OEM Style or 20mm raised version? If your car is lowered, go with the 20mm raised version. There are no negatives and it fixes up bad axle angles which cause blown cv's. Vehicle Compatibility: - Scion FR-S - Subaru ZC6 BRZ - Toyota ZN6 GT86 Note: on SUPER low cars running the 20mm risers your axles may then come into contact with the rear upper camber arm and or subframe which must be notched accordingly. It's uncommon but not impossible. This is not an issue at all with the OEM style solid bushes.