The Optisan EVR ED 10x42 Binoculars boast 93% light transmission and a Japanese optical design that produces clear imagery while greatly reducing edge distortion and chromatic aberration. This close-focusing optic is useful for bird watching as well as viewing insects and butterflies. They are IPX7-rated fog and waterproof, and nitrogen-purged to protect the glass elements. The twist-up eye cups, ocular lens caps, and objective lens caps are all removable.