Every welding O2 supply house I have been to exchange the cylinder, not re-fill it. It is just so much faster for a welder that needs to get back on the job. This exchange would be only for standard sizes. This may be fine for your glider but in my particular case (Schleicher) I haven't found a welding supply house yet that has the correct (exchange) size for my sleeve. Most glider operations out west can refill for you. You might try medical supply houses.