Here's what other sites are saying:
Fits standard fuel bottles and allows for easy, safe, and clean transfer of fuel from bottle to stove, eliminating the need for a funnel. Turning the top opens the spout and a finger controlled air vent allows fuel flow to be regulated. The top seals tightly for storage and transportation. Weight 1/2 oz.
- Vargo Outdoors
Designed to fit MSR and Sigg fuel bottles. The fuel faucet eliminates the need for separate caps, spouts and funnels. When you need fuel, turn the top to pour, turn again to seal without leakage. Wt. 1/2 oz.