The evolution offers superior pressure distribution, positioning stability, comfort and simplicity.  This makes the Evolution Varilite's most popular wheelchair cushion.  By adding Varilite's pressure setting valve (PSV) we've made the Evolution even better, taking the guesswork out of cushion adjustment.  Users and caregivers value its low weight, comfort and ease of use. Fabric Evolution foam is bonded to two-way-stretch knit fabric for maximum conformity and during immersion.  The fabric is puncture and water resistance.  Valve Evolution PSV uses Varilite's revolutionary new pressure setting valve.  Sitting on a fully inflated cushion, the user or caregiver opens the PSV to a pre set position.  When the PSV senses that the desired level of immersion has been reached, it stops releasing air.  The user then closes the PSV.  The Evolution is available as an alternative with traditional two-way valve Varilite valve.  Sitting on a fully inflated cushion, the user opens the valve when sitting approximately 1/2 inch (13mm) of air and foam, or when two thirds of the air has been released.   Quantity 12345678910 Price (ex VAT): £293.51 Price (inc VAT): £344.87 Options and Accessories your cushion size: 12 x 14 14 x 14 14 x 16 16 x 16 16 x 18 16 x 20 17 x 17 18 x 16 18 x 18 18 x 20 20 x 16 20 x 18 20 x 20 your cover style: Incontinence cover Mesh cover