Aeron Chair - Highly Adjustable Titanium Frame by Herman Miller

Lumbar latitude (optional): The lumbar pad can be adjusted vertically through 4 1/2-inch height range. Its depth can be set at 3/4 inch or 1 1/4 inches.
Very low to very high: With its pneumatic lift, the Aeron chair has an unprecedented seat-height range-from a low of 16 inches (on the A-size chair) to a high of 20.5 inches (on the B and C sizes).
Tension: the good kind: The tilt-tension adjustments lets the user easily control the resistance felt when leaning back.
A breakthrough in tilt dynamics: The Kinemat tilt mechanism allows the body to pivot naturally and simultaneously at the ankles, knees, and hips providing a smooth ride and proper support from forward-leaning to reclining postures.
A completely new suspension system: With its unique Pellicle material, the Aeron chair distributes weight evenly over the seat and back, conforming to each person's shape. The material also lets air pass through, adding to long-term comfort by preventing body-heat build-up.
The arms have it: Chair arms have never before been this adjustable. Independently, armrests pivot inward 17.5 degrees for keying and outward 15 degrees for mousing. Arm height adjusts independently within a four-inch vertical range. (Adjustable arms optional).
Limits without locks (optional): The tilt limiter allows the user to control the tilt range without being locked in a single position.
Onward and forward (optional): The forward-tilt adjustment positions the seat angle 5 degrees forward, a posture favored by many computer users.