Kinetic responsive. Sound is vibrations. Vibrations move better through dense objects that less dense ones. What does this mean, well it means you can finally get that sound that you have been looking for. Rubber is very low density, but a block of steel is really, really dense. Now which one will make a better bell? The Rubber, being soft, and low-density will make a sound when you stick it but will dissipate quickly, no sustain, no brightness. The Steel will allow the vibrations from the strings to travel better, faster, and will let your sound cut through the mix like a chainsaw cutting through cotton candy.