Here is one more example. This time we used a cheap 15mm spacer one would commonly find at the local wheel/tire shop.
Traditional Rounded Wheel Spacer - 15mm 5x120 72.56mm CB
End Result - 1.2 lb
Verstraβe Motorsport Wheel Spacer - 15mm 5x120 72.56mm CB
End Result - 0.6 lb
That is savings of over a half pound per spacer. That is a total weight savings of 2.4 lbs for all 4 wheels, a rather significant amount of rotational mass shaved off.