Waterproof performance for inclement weather  All MONARCH Fieldacope models can be used without worrying about changing weather conditions in the natural environment. The MONARCH Fieldscope bodies are waterproof*, sealed with O-rings and packing seals that make them airtight. In addition, the body is filled with nitrogen gas to prevent fog due to sudden temperature changes. *Waterproof (up to 1 m. for 10 minutes) (NOT designed for underwater usage)