Made from a triple layer of breathable semi-rigid material (polyamide, foam and polyester), it has a lumbar plate with belts and buckles for fixing in the chair back, belts passing under the buttocks towards the perineum, holding the thighs from the interior towards the hips. The thigh straps start at the inferior ends, with ratier belts at the ends, and buckles and adjusters to fasten and adjust.