Much the same way as an operation in the field can be unpredictable, so is the accompanying terrain and the conditions your eyes will face. Wiley X Changeable provide the flexibility of a multiple lens package (Unique SlotT technology simplifies lens changing) and durable, battlefield tested frames, so you're never caught unprepared. All shatterproof Changeable styles meet or exceed ANSI Z87.1-2003 High velocity impact safety standards.