These shock-absorbing pedestals are our best seller, and are designed to accept your spider/slider which fits over a 2-7/8” OD standard pedestal tube. This allows 360° swiveling. The round base is a standard 9-¼” OD with a 6-hole bolt pattern. Proper operating range is between 140 -275 lbs total seated weight. Please consult the factory for heavier or other special applications.