pfft... people still use those things (1 pound propane cylinders) in the 21st Century?
Propane Tank Cylinder, aluminum, 10 lb. capacity, 16.5" x 10.5" - REFILLABLE - Put a Y-splitter on it and you can fuel a couple devices at the same time, like a stove and grill, or heater. Since it's just me, although I often prepare food for a crowd and I have an efficient Partner Steel stove, it usually provides sufficient fuel for 2 years before recharging.
The argument that 1 pound DISPOSABLE cylinders can be refilled is null... they can't take a full charge with home equipment and can't, by law, be refilled by retail gas suppliers.
I encourage you to ditch the "little green mortar rounds". It's a one time purchase that'll last you a lifetime and serves other uses, i.e., back up fuel for the home grill when the "Blue Rhino" tank unexpectedly runs dry in the middle of grilling. Buy once - cry once.