Set of used Dinan Performance Lowering Springs + Supplemental Ride Quality & Handling Kit (basically bump stops). Both together cost $420 new.
Springs had been on the car for <2 years and ~15K miles. They work on all 550i years and variants (RWD and xDrive).
One of the boots from the bump stops tore when I was uninstalling it, but the bump does take standard BMW sized boots.
Asking $230 shipped.
I forgot to take a picture of the car before being removed, but here is Dinan's official 550i with the springs on and 20 inch wheels.
