Finally, a ballistic spectacle designed for use with and without over the ear hearing protection and communications systems. The Aegis Echo is designed for anyone who has ever felt the “rage” of their temple and helmet combination digging in over hours of use. Once you wear the Echo, you will wonder why you use anything else! Good fit for hat size 7 1/4 or less. Meets US Standard MIL-PRF-31013, ANSI Z87.1-2010 & EN 166 standards.