These high quality waterproof nitrogen filled observation binoculars feature bak 4 prisms and a multi coated optical system that allows for 92 light transmission and distortion free images built into the binoculars is a tripod mounting bush and threaded eyepiece units to allow for filters the long eye relief and fold down rubber eyecups make these binoculars suitable for spectacle wearers the helios apollo 20x110 ms observation binoculars are suitable for medium to long range terrestrial a