The high part in the back that goes above your heel behind your ankle makes this great for mountain trail running. it makes a snug fit around your ankle so less rocks, thorns and and sharp grass gets inside your shoe. The mesh material is pretty tight and it does not allow small particles to get inside. Here we have a lot of cheatgrass, which has these sharp seeds that stick through your socks, they get down inside your shoes, they poke through most mesh materials and end up stabbing their way through mesh and into your shoes, but I have not had any get through these or end up getting down inside through the ankle area. There's no flat areas out here to run on so every thing is either an incline or decline and these stay on tight and dont slip off like the way most other sneakers do.The main reason for the 4 stars instead of 5 is they are 100% thin lightweight plastic and feel like they wont last very long. Don't wear these around a camp fire, one small ember and they'll turn into napalm