These boots are excellent for use in the flightline heat. The rubber soles are soft and comfy. The ventilation on thes things is 10 times better than the standard hot weather boots issued. I had a pair of these for a 6 month deployment and used them everyday on the flight line in 120 plus heat! My one and only issue with these boots was the liner behind the zipper. It was to short for my size 9 1/2 foot to slide out because the laces where tight due to my chicken legs. Whats the point of buying zip sides if you need to untie the boot any way? So I just removed the liner and all was well. If not for the liner being there this would be a 5+! Hope this helps.