I bought a few today (for $1.50 each, what the heck). I got the 40mm "Optimzer" model. The larger size "Moderators" (50, 60, 70, 80, 90mm) are designed to reduce overtones. Nothing wrong with that, if the situation calls for it. I know lots of guys who put some moon gel or tape on their cymbals in certain situations. The Cympads will certainly make this easier, and more asthetically pleasing.
The smaller size "optimizers" that I bought are 40mm, and are the same diameter as a standard cymbal felt, and are designed to replace your standard cymbal felts more so than "modifying" your cymbal sound. I found that the 40mm "Optimizer" was about 2/3 as thick as a large Gibraltar felt.
I haven't really gotten to try them out "full scale". I just lightly tapped a K Constantinople ride, and couldn't really tell a difference at all. I will say they are cool and are certainly more durable then regular felts. I am interested to see what the effect is on a small splash. I am not at home now, but I will report back once I get to do a "full scale" test.
Anyone else used these before? Impressions (apologies to Coltrane)?