Barr & Stroud Roof Prism 10x42 Sierra Binocular: The Barr & Stroud Sierra 10x42 binocular has an extra 2x magnification over the other 42mm objective lens model in the Sierra range. This additional magnification can be helpful to get you closer to the action but there are trade offs. The extra magnification means that not quite as much light gets through to the observers eye as in the 8x magnification model.
The Sierra range from Barr & Stroud feature rugged construction combined with brilliant optics. They are waterproof to a depth 1.5m of water for three minutes. The binoculars are filled with nitrogen gas which keeps water out and also stops the optics suffering from internal fogging in unfavourable weather circumstances, this Barr & Stroud Sierra 10x42 binocular is truly weatherproof.