This trail is about 16 miles, not sure how the description has 21. It contains a perfect amount of vertical ascent to make one suffer on the descent. There is enough scrambling and route finding to be challenging and keep you on your toes. Great destination run for experienced runners and mountaineering types. This route has class 3 and 4 scrambles. You should be skilled at rout-finding and mountain running. Finished in about 5:30 but I felt like I was moving pretty good with no stops. Others have finished in 4:15 (the big kids) or 15 hours if your VO2 is average. This is a pretty big day. Prepare accordingly. Oh yeah this route had 7,900 vertical ascent. Hope that helps. There could be slight variations depending on if you stay on the ridge or take the trail. The ridge is cooler. Take the free bus home or call a friend.