The Novibra GK Block is specifically used for isolating equipment where low interfering frequencies are encountered. They are typically used under concrete foundations supporting either source or sensitive machines. The highly specialized rubber compounds used, unique geometrical shape, and carefully controlled load deflection characteristic make the GK Block an excellent lower cost alternative to installations normally required to reach system natural frequencies as low as 4Hz. GK Blocks are rated from 4,000 to 18,000 lbs. Printable Copy