Trangia Simmering Ring
Here's what other sites are saying:
The Trangia Spirit Burner is the most versatile and user friendly alcohol burner on the market. Besides having a track record of reliable service that spans decades, it also has a couple of uniquely useful features. The simmer ring allows the burner to adjust from full to simmer and extinguishes the flame when closed completely. The twist on cap with o-ring seals the burner so you don't have to empty unused fuel between uses and prevents evaporation - less fuel wasted means less fuel you have to carry. Includes burner, simmer ring, and cap w/ o-ring.
- Mountains Plus
The Trangia Simmering Ring makes it easy to moderate the flame eminating from your Trangia Spirit Burner. Move the slide far enough, and you can use the Simmering Ring to extinguish the flame.