Robust plastic fuel bottle for various kinds of fuel. Branded "Trangia" I assume it is meant for suitable fuels for the spirit burner such as methylated spirits. The neck is reinforced with a metal band so that the screw in valve assembly won't split the neck over time. The valve itself is easy to operate and can be 'locked' in the closed position to avoid leaks. New valve assemblies are available to buy separately should the need arise. The whole thing seems well engineered as you would expect from Trangia. I bought mine online from Base Camp Food as they were offering the cheapest price + postage. Their service was great and I would use them again.