Update: I received my new Comfort Company Liberty X wheelchair cushion this week. And.....surprise, surprise my post of 9/29 is wrong, as there was NO valve leading into the gel portion 'to release air when you sit on it'. I contacted Customer Service and was told that the valve was discontinued about two years ago. I pointed out that the video on-line specifically pictures a valve to open and close - I suggested they update their video and the fellow said he would 'contact the marketing department'. Also, on the underside of the gel part of the cushion there's a statement "Read User's Manual". No user manual was enclosed in the box - told cus. ser. fellow. You just sit on it and let it conform to your bottom.
On the plus side, this new cushion is not flat as a pancake as was the sample cushion I had used, and after one day of use it feels pretty comfortable. I cannot recommend it though, as I have sensation and don't know if it would also be suitable for someone who had sensory loss.
P.S. I understand Comfort Company has been under Permobile for two years.