Herman Miller 3 Lever Aeron Mesh Office Swivel Chairs. Ergonomic Size A  Which is a Smaller Size Black /Grey. Max Seat Height  50cms . Price is for each chair 3 available plus I have other Sizes on other lisings 
These Chairs are considered to be one of the best chairs on the market.
The Herman Miller chairs are in a good condition minor marks only. Odd minor paint chips to frame Read up on chairs and see the outstanding reviews 
They are Height Adjustable. And have  seat tilt  button one for back tilt and one for front tilt.. the arms are big for comfort. And with Tension  control The chairs are built for maximum comfort. Built in lumber support on the back. Mesh back and seat. Brilliant chairs at a good price