Kneeling shifts weight off the lower back and onto the shins, and the curved birch plywood runners under this frame add a rocking arc of 60 degrees forward and 30 degrees back so the position never locks up. The seat cushion measures 15.5 by 12 inches and the knee pad 18 by 10.5 inches at 4 inches thick, filled with high-density sponge and wrapped in breathable fabric. Crossbars tie the two runners together, which is what lets a backless frame hold 265 lbs without flexing. Because there is no backrest or gas cylinder, the whole chair weighs 14.5 lbs and lifts with one hand. Its footprint is small too, 28 by 18 inches and 22 inches tall, so it slides under a desk when the workday ends. The backless shape leaves the upper body free to move while the birch wood base rocks. Fabric-covered padding cushions both the seat and knee rest at a study or office desk. Net weight: 14.5 lb