Herman Miller Equa swivel , tilt , height adjustable office / desk / task chair . Designed by Bill Stumpf and Don Chadwick who famously 10 years later collaborated on the creation of the Aeron Chair . Not sure if this is black or very dark slate gray . Upholstered seat sits on polished cast aluminum base . Chair adjusts up by spinning the seat counter clock wise . There is about a 3.5" adjustment seat height can go from a height of 19 down to 16 high . Overall height 35 down to about 31 . Seat cushion measures 20 wide x 19 deep . The chair is in good condition bases have some typical scuffs at outer ends above the casters .