I was unsure about this purchase, as I was unable to find any reviews anywhere about these pants. I just got them today, so have not actually used them yet, but wanted to do a small write-up for others that were in my situation. First off, they are Summit Series, so they are very clean and have a very nice finish to the pant, they look very nice. I would say they are along the lines of an alpine\performance fit. I am 5-8 135 athletic build and the small fits me perfect, and I mean perfect( I wear a 30x32 in all of my other pants). These pants could not be tailored to fit me any better. They are very light, yet seem to be tough, and have some nice stretch to them. Definitely a running, hiking type pant. I am sure they breath well. I will be putting them to use in the next day or so and will do an update after I have used them. At $100 they are a bit pricey (probably a bit extra for that technical look and the summit series insignia), but once I tried them on, there was no way they were getting returned. I do not have the TNF Running pant or Prolix Pant, so can't really compare. I like these pants and would give 5 stars if they were $80.
I have been running in these and wearing them to the gym, fantastic pants, very breatheable.