Converting to gas?
The Endurance Gas Burner Converter fits all Trangia stoves, and has the advantage of having a smaller gas tap, making it easier to insert into the base of the stove.
Trangia 25 or 27?
Contrary to what you might expect, Trangia 25 Series is the larger cook set, and 27 is the smaller. Most group leaders choose the 25, as it cooks for 3-4 people. The 27 only cooks for 1-2.