We have designed 2 generations of pillows using 8 types of bladders.  The first generation of bladder valves had a long cylindrical valve.  The Gen 2 bladders have a red "button" in the flat valve and can be positioned to the "open" position to let air out and the Gen 3 valve is a yellow button on the flat valve which is always in the 2-way passive position that keeps air in the bladder, until you push it to let the air out for storage.

• Gen 1 bladder = cylindrical valve to screw down to keep air in.
• Gen 2 bladder = red adjustable button that can be screwed down into the "open" position to let air escape and popped "out" to keep air always in.
• Gen 3 bladder = yellow button that is always in the "out" position allowing you to breathe air in and push to release air.