Keys, The Critical Mass platform is terrible. You can get a MinusK platform that will handle that weight but You won't like the price. The KSI platforms are also great but probably even more expensive. Critical Mass and Townsend make inexpensive, 1/2 baked stuff that no respectable lab would ever put an electron microscope on. A turntable's requirements are just as stringent. If a lab won't put an electron microscope on a certain platform you do not want to put your turntable on it. Cheap solutions are just cheap and frequently worse than no solution.