Howlin' Prescription (Rx) model. A rounded aviator design crafted from premium acetate, fitted with superior polarized performance lenses from the world leading manufacturer of prescription lenses Essilor. They come with an optional headstrap for sporty pursuits. Whether you're trail running, kayaking, sailing, or climbing, the headstrap guarantees your sunglasses stay on at all times. The goal was to create functionality at its best-looking - a pair of sunglasses for every occasion - and the bestselling Howlin' are proving to be the most versatile sunglasses on the market.