The Metron SP High Density Wheelchair Foam Cushion is a perfect fit for most wheelchairs. It has a lightweight design as well as ties on the back to allow the cushion to be tied into the wheelchair for a secure fit and feel. Multiple sizes available in either 16" (40cm) or 18" (45cm) and also 2" (5cm) or 3" (7.5cm) Thickness. Meets CA117 standards.