Two groups of air bladders inflate, then slowly deflate in this alternating cushion to stimulate circulation and relieve pressure to skin and underlying tissues. The SofTech Basic cycles every 60 seconds and runs for more than 25 hours per charge. The system is contained inside the cushion, so nothing needs to be mounted on the chair. Operation is easy: just a single power switch. The cushion is available in 16x16", 18x18" and 20x20" widths/depths.