Just thought I should post this as I have had 2 valves fail in 1 months time. The valve has a rubber flapper inside for the check valve to operate, With pressure in the tank they press on the cone side to shut off the air and with prolonged use and storing them with full air tanks in between flights the rubber has failed. I only found this as I was pulling into a parking sapce and had the plane in the back of my van and heard the pressure release. Had this happened in the air I would have lost brakes on landing or worse gear down and locked when needed. I just wrote off the first failure as a fluke but will now be replacing them with BVM filler valves.