In my case the previous owner supplied new stock bearings so I had new round steel mushroom inserts to fit between the bearing and the body. But if your old fasteners are rotten and rusted then you will need new inserts as for some reason these are not included. The instructions require these missions. Large shims or no inserts at all can be used with this 1" riser kit as it does not flex much and the poly material is slightly stiffer than the OEM rubber. Otherwise it's a good kit that will last a long time. Pretty easy once I line up the holes. My tub was completely ripped off the frame, but if you're just doing a direct swap, the instructions say you have to do this one side at a time to keep the screw holes aligned. Revain had the best price and free shipping so far.