The only sure thing about any environment is that it will change temperatures, moisture and lighting conditions can all fluctuate from one minute to the next. Engage binoculars were built from the inside out to deliver world-class performance every time, in every condition. The glass captures bright, clear images while preventing glare and actively repelling water, oil, dust and debris. The locking diopter permanently secures the desired focus setting, no matter what. The rugged chassis is built to take a beating, so you can maintain focus and engage on what's out ahead.