Originally Posted by russc
Get a 20oz, some stainless braid and two on/off ASAs. It's very easy to fill 3.5oz tanks yourself. You just need to either freeze the 3.5 or chill it by venting co2.
Why would you need to chill it? And when? Before or after filling it? Sorry for the noob questions, just curious. I have never filled a CO2 tank myself and can't really recall someone doing it when filling one at the fields.