Instruct: Classify the given review as either positive or negative.
Query: Not up to the task.

They fit MSR bottles OK, but are a VERY tight fit in SIGG bottles. When first installed, the caps leaked, it only got worse from there. The caps would not stop leaking not matter how tight they were screwed down. When opened and pouring, a pretty good trickle of fuel would run out around the outside of the nozzle opening and make a dangerous mess around your lantern. But, the worse part was that within a very few minutes of getting a little white gas on the two o ring seals, I noticed that the black o ring material was coming off on my hands. The rubber is NOT white gas compatible! I removed both of these and discarded them. Trangia makes a much better bottle valve, also available on Amazon.