High quality waterproof nitrogen filled observation binoculars with individual eyepiece focusing designed for medium to long range terrestrial and astronomical observations incorporating bak 4 prisms and a fully broadband multi coated optical system the 15x70 model feature a central focusing cf and an integral tripod bush the larger 20x80 and 25x100 models feature individual eyepiece focusing if and a central stabilising bar with sliding tripod adaptor for optimum balancing on a trip