After researching and reading the multitude of reviews extolling the virtues of risers for subwoofers I decided to take the plunge and buy 2 of these units for my newly acquired SVS PB10-NSD's. And as many of the other reviewers state, there is a marked improvement in the tightness and depth of sound once the risers are in place. The Auralex Grammas almost match the dimensions of my subs exactly. The fit and finish of the risers are first rate (if a little rugged looking). I do however think they may be a bit overpriced considering the materials used in the construction. Overall I believe these are a must have for anyone owning a subwoofer. Your neighbors will appreciate that you got them (almost as much as you will).