Most sunglasses will perform well during the first two or three miles of an intense hike or trail run, but seven or eight miles of intense moving will really separate the wheat from the chaff. In order for a pair of sunglasses to perform during the entirety of your run or hike, they need to be specifically designed to do so, and the Bliz Force Sunglasses with Bonus Lenses most certainly are.Housing a load of features that will make these sunglasses comfortable from the first mile to the last step, the Force Sunglasses will make your high aerobic pursuits more comfortable thanks to their carefully considered design and thoughtful accessories. The lenses are interchangeable to accommodate changing light conditions and they block UV rays for extra protection from the sun. The polycarbonate lens material is treated with a hydrophobic coating to resist fogging and is also scratch resistant and shatter proof, so you can run through thick trees with ease. Comfort is key to any pair of sunglasses, so Bliz threw in adjustable temple and nose pads to fit the exact contours of your face, then added a removal sweat bar to absorb sweat. Bliz also included its unique click in head band to prevent the sunglasses from sliding down your face when you're forced to watch your footing on technical sections of trail. Proposition 65 Warning for California Consumers: This product contains chemicals known to the State of California to cause cancer andor birth defects or other reproductive harm.