I use something called the Angler 2 whch is very similar. However, I got one of these from Quilt in a Day, and I really like it. You set the edge in front of the feed dogs, so you don't need a "key" to position it. And they include reuseable adhesive pads to stick it to your machine.
http://www.quiltinaday.com/shoponline/notion/66669