I, too have the original Grace frame - from a friend. It has 2 black tracks that are continuous, but I still have the black plastic carriage. For the most part it does a great job, but I have trouble with smaller curves. Sometimes my curves/circles get squared off. It almost feels like the carriage gets stuck for a stitch and I am not in control of it for a second. I choose my quilting designs around the little problem. It sounds like some of you are saying that the wooden carriage works better. My DH has been trying to come up with a way to smooth out my system. I may need to start a new thread, but if anyone has a suggestion, I'd love to hear it.