AWESOME! :bowdown: The difference is hard to describe. There is a response increase and overall less looseness within your strut assembly. They also enusre a more precise, correct alignment under heavy cornering as they will not flex nearly as much as the stock STi (or wrx) mounts. The install is straight forward if you have done springs before. If you take a key, you can effectively poke the mounts. You will notice a difference where it matters. If you are planning on getting springs, these are definately the ultimate item to pair them with. "Low compliance Group-N strut top mounts ensure precise alignment control under heavy cornering forces while also being more resistant to coming apart under severe use such as rally and rallycross. Tightens the handling feel and improves steering & suspension feedback. Strongly recommended for any upgraded suspension kit that uses factory top mounts." These are a must do with any aftermarket spring setup :bigthumb: