Subframe mount inserts for the F22 2-series, F30 3-series, and F32 4-series are a great way of stiffening the rear suspension without having to completely remove the subframe and press out the original mounts. These inserts are like spacers, filling the voids on the top and bottom of the stock rubber mount, and restricting excess deflection and movement. This makes the whole rear suspension stiffer but since the rubber mounts remain in place there is no sacrifice in ride quality, noise, or vibration. These will also help the stock rubber bushings last longer since deflection is limited.
Powerflex has designed these bushing inserts to be a direct fit to the factory subframe mounts. The subframe will need to be partially lowered to gain access to the top of the subframe mount. Once lowered the inserts simply slide into place and refit the subframe with the factory hardware and retaining plate. In most cases an alignment is not required.