I have these as well in mine, as VGP said, massive improvement in turn in and mid-corner stability, the car doesn't feel as floaty as with stock suspension, while the suspension is definitely stiffer, the car doesn't feel like its crashing over bumps, more of a solid thud, if that makes sense.
They are a fairly simple set-up, an inverted Bilstein gas mono-tube shock (made to H&R specs) coupled with H&R springs, the only adjustment available to the end user is the ride height.
These are probably one of the softer variants of coil-overs available as they are marketed to street & occasional track use, a lot of others on the market are more track specific (eg. BC coilovers) and will shake the fillings from your teeth, from what I have read.
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