Two cushions do all the work here, one 16 by 11 inch seat pad 3 inches thick and one knee rest sitting 13 inches off the floor, and together they tip the pelvis forward into an upright posture that keeps the lower back from rounding. The base is a pair of curved solid wood runners joined by a reinforced crossbar, so the rocking motion stays smooth and the frame holds 330 lbs. Polished surfaces feel safe under bare hands and leave hardwood floors unmarked. Gentle rocking keeps blood moving during long stretches of desk work and takes the edge off stiffness. Without a backrest the chair measures 21.5 by 34 inches and stands 22 inches, and at 17.5 lbs it moves easily between a home office and a meditation corner.