Like all my Vargo gear I've accumulated over the years, the design of this device is flawless and the result is unbeatable functionality.
The moveable arms allow the filter to fit nearly any size cup, but they're sturdy and they seat perfectly on the lip of the cup without any need to hold it in place. The little D-ring really is a nifty, foldable handle that doesn't heat up at all. The double-mesh construction makes for remarkably un-muddy coffee, regardless of coarse or fine grind. The cone size and amount of ground coffee it holds are perfectly dialed -- making just the right amount without allowing your boiled water to get cold. It fits perfectly into my Vargo coffee cup; the BOT pot and other Vargo containers easily accommodate the filter plus coffee and stove. I find it super easy to clean with minimal or no water.
If you're serious about your coffee or just drinking it to get up and going, this is the best way I've found to make it on the trail.