YouToo offers the same revolutionary back support as the You chair. The back raises and lowers to the ideal lumbar position. This totals to a 3.54” travel with the dial and Back Height Adjustment Mechanism combined. Optional OHC (carpet) and OHH (hard surface) casters provide the ability to adjust the tension in the caster, giving the ability to control the rotation on various surfaces. Tension adjustment can be done on each caster with a phillips screwdriver, simply turn until desired tension is reached. Overall [Synchro Tilt]: 39.5" - 43" H | 28" W | 28" D Overall [Dynamic Synchro Tilt]: 39" - 42.5" H | 28" W | 28" D Seat [Synchro Tilt]: 16.25" - 19.75" H | 20.25" W | 18.5" D Seat [Dynamic Synchro Tilt]: 15.75" - 19.25" H | 20.25" W | 18.5" D Back: 22" H | 18.5" W