pavement, gravel fire roads, stream crossings, technical single track - these shoes can handle it all. the fit: even with wide feet i ended up a half size down than what i normally wear. very nice snug fit from the heel to the middle of the foot (without feeling like the shoe was strangling my feet). this fit allows the shoe to keep your feet in place and prevent them from sliding forward/smashing into the front on steep downhill descents. and of course this shoe features a wide toe box that merrell is known for. observations during use: despite the looks and the build this shoe is incredibly flexible and responsive unlike other similar trail shoes i've run in. the 4mm drop allows for a fantastic natural running experience. even over very rocky technical terrain i felt connected to the trail below me without feeling discomfort from stepping down on jagged rocks and roots thanks to the rock plate and cushioning in the sole. this allowed me to really focus on moving down the trail without the worry of stepping in the “wrong place”. the aggressive lugs/sticky rubber on the sole also gripped very well on all trail surfaces (wet or dry). these shoes took the beating over and over instead of my feet which is exactly what they were made for. even after a 31.1 mile run in the shoes my feet felt fresh and comfortable. these shoes would have no problem tackling longer ultra events (50 mile, 100k or 100 mile). the waterproofing worked flawlessly and kept water out while running through creeks and streams but didn't overheat my feet like i've experienced with other waterproof shoes. final thoughts: as long as merrell keeps making shoes like this; i'll keep knocking out trail mile after trail mile in them.