Unfortunately the locker on my boat only accommodates the little 10 pound aluminum tanks, but if I could fit one, I'd be tempted to get one of those composite (see-through) tanks... no corrosion... easy to tell how much is left... cheaper than aluminum. I haven't ever seen them in the smaller sizes though. They sell the bigger ones at Amazon and also Defender though... way too much work to modify my propane locker though. I found a place that refilled my expired tank this season... (yes... buyer beware... I know)... but that solution isn't going to last me forever... so I'm likely going to end up tossing out a perfectly good aluminum tank soon and buying an identical replacement with a newer date stamped on it... frustrating at the prices they go for. The only concern I'd have with composite is whether it would melt in a fire situation... but It would have to be a pretty major fire before that happened on my boat, and by that point, the propane hose connected to it would likely have melted anyway. It's far enough from my galley and/or engine compartment (most likely sources of fire) that I'm comfortable with that minimal increase in risk.