BMW 1 Series F20, F21 xDrive (2011 - 2019) Rear Diff Front Bush Insert - PFR5-1927 This is a polyurethane insert that fits into and fills the voids in original bush to stabilise the diff under acceleration. - NOTE: Price is for CAR KIT, NOT per bush… Powerflex price their bushes individually, but we have combined the quantities to make it simple!