The bag is just long/tall enough to fit a Tribe mat, but only if the latter is quite tightly rolled up. It would be nice to see a design in the future in which there's a bit more space lengthwise.
The issue with the current dimensions is that the mat tends to unfurl inside the bag, especially if its wearer is being active. This has the effect of undoing the clip which keeps the bag closed. You can prevent that by tying an additional knot right next to the clip, but I feel that this should not be necessary.
Otherwise, I am nothing but pleased with the bag. The quality of the material is good and although I have not owned it for long yet, I expect it will last a long while.
Thank you for your constructive feedback, and we will follow-up with the manufacturer to see if they can extend the length of the bag when they design a new version.