What I really like about them is the full coverage they offer, giving good field of vision, aerodynamics and excellent wind coverage. I do hate eyewear that makes your eye water when you go ride into a strong headwind, or when you start to boogie going downhill. The Dirt offer incredible wind protection, almost like wearing a pair of goggles. I think wind protection is due to the large lenses, wrap around frames and that they sit close (but not to close) to your face.
Another per peeve is lenses that fog up on you, like when you go into a dense section of trees that might be humid, after a rainstorm, or when you start sweating, and then pop into a cold spot on the trail. The Dirt never seemed to fog on me in any of the adverse conditions that I dumped them into, so the anti-fog coating works amazingly well. The side sun coverage that the frame offers are quite nice, and cuts down on eye fatigue and scattered light entry, and the frame and lens curve around enough that the sides don’t interfere with your peripheral vision. The curve and shape of the frame, along with rubbery shock absorbing nose and ear coverings, keep the sunglasses stuck to my head no matter how rough the terrain tossed at me. They fit nicely within helmets, but bow out a bit much for a full faced helmet. With any pair of sunglasses, I can never decide whether to wear them under or over the helmet straps? They have been comfortable, with a nice fit and feel. One issue is there is no adjustability since the frame is not pliable (stiff frames) nor offers any adjustment features.
Thanks to the durable NXT, the lenses have been bombproof, and I have gotten no scratches, which is pretty amazing, since I always seem to do that with any eyewear, even the ones that are supposed to be unscratchable (marketing hyperbole). They have excellent varying light capabilities due to the Zebra photochromic lenses, and the amber tint has been especially nice on the cloudy and foggy days. Sometimes buzzing in and out of trees in the bright afternoon sunlight the lens did not change fast enough for those conditions, but it is a very minor issue. If I was doing a lot of desert riding, or was going to be constantly out in bright sunlight, I might prefer a somewhat darker lens. I usually ride in places in which I am going in and out of the shade, into wooded areas, and I also ride a lot in the late afternoon, so I appreciated the photochromic lens. The lenses have phenomenal optical quality, and they’re distortion free with a high degree of clarity. The lenses are large and curved enough for a nice panoramic field of view.