This adjustable-angle stool allows the sitters knees to be lower than their hips, which makes it easy to achieve an upright, buoyant, well-balanced S-spine. In contrast, most chairs force the knees to be slightly higher than the hips, which, in the situation of desk work, is a recipe for a strained, compressed C-shaped spine. When the knees are lower than the hips, there is no need for geometrically combative lumbar support inserts.