Odd, the link works for me just fine. They are Front Lowering Spring Perchs. Basically let's the suspension up into the engine a little more, hence drops the front.
According to the site...
"Front Lowering Spring Perch BMW
Will NOT work with coilover kits
***Spring perches lowers car approximately 10 - 15 mm or (0.4 - 0.6")***
-Want to lower the front of your car, but keep your factory/OEM suspension?
-Want to lower the front end a bit more, after adding aftermarket suspension (non-coilover set up), but can't do it
Factory/OEM fitment- - to be used with shock and spring combination (oem or aftermarket)."