Smith PivLock Asana Sunglasses. The Smith PivLock Asana multi lens sunglasses feature a sleek, feather light design that's perfect for small to medium sized faces. These sunglasses are loaded with features that make Smith a leader in performance eyewear, such as their revolutionary PivLock interchangeable lens technology. Swapping out lenses has never been easier as you simply rotate the temple 45 degrees to remove the lens. Not only that, the PivLock design ensures an unobstructed field of view an important feature when you're speeding along on your bike. The trio of lenses have you covered for the widest array of light conditions from the brightest sunshine at one extreme, to varying light conditions, to riding in the rain or at night with the absence of light at the other end of the spectrum.