The 500AP Series vibration-isolating leg stands from Kinetic Systems, Inc. (KSI; Boston) support KSI breadboards and optical tables, and are available individually as modular mounts or as leg stands with braces and casters for optical tables. Their proprietary internal trifilar and quadfilar pendulum systems provide exceptional horizontal vibration isolation; when combined with active-air suspension, it gives users protection against horizontal and vertical vibrations. The leg stands can be configured to incorporate automatic leveling. They offer low natural frequencies — 1.25 Hz along the horizontal axis and 1.50 Hz along the vertical axis. They can achieve isolation efficiencies of 98% (horizontal) and 95% (vertical) at 10 Hz and above. The trifilar and quadfilar leg stands can support equipment weighing 500 to 2,000 lbs. and 250 - 1,000 lbs., respectively, isolating them from ambient building vibrations. Both types are Class 100 cleanroom-compatible, and braces and casters are available for leg stands from 14 - 32 in. high.