Ok just played through a cd without, with small isofeet and with the large 45mm dia isofeet with 8mm dia balls .....

Its clear these do more than the smaller units....by a small but significant margin.   These are an absolute winner !

I've had stillpoints under the quad 99 without them making the slightest difference.....also sorbothane pucks,  vectuer cones,  tender feet   large and small ....none have had the impact of these .....