Swivel Chair Manual Mechanism: A surprising high quality low cost and fully featured mechanism. This 360 degree swivel and tilt chair mechanism is constructed of extra heavy gauge steel. The smaller footprint size makes it ideal for retrofitting and using a Mounting board as the mounting holes usually will not interfere with original mounting holes. • Large forward tension adjustment knob • Generous height adjustment • 360° swivel ability • Compact • Economical • 1" OD threaded post x 9" • Bottom 3" Post unthreaded for stability. Front to back mounting hole to hole measurement-7 1/4" x Side to side (at centers)-4"