I'm selling a replacement rolling, height adjustable desk/office chair base that is CLEAN, the wheels are free from debris/roll easily, and is in ready to use condition ! The base plate holes measure 8 in. X 6 1/8 in. on center, the legs measure apx. 24 in. across, and it appears the max height adjustment on it from the floor is apx. 18 in. This is a very easy way to replace your desk chair base that keeps sinking because the pneumatic gas tube is shot. These replacement desk chair bases including the base plate and pneumatic gas tube on Amazon new cost on average $55 to $65. To replace the pneumatic gas tube only new on Amazon costs on average $18 to $25. I'm asking $10.00 for the whole unit.