The first thing that strikes you about binoculars, is the apparent difference in two basic types of designs. All binoculars either use “porro prisms” or “roof prisms”. The ones using porro prisms are the traditional design where the eye pieces are off center to the barrels. In the case of the ones using roof prisms the eye pieces are in line with the objective lenses and have a sleek design. The advantages of porro prism binoculars are cost (less expensive) and the greater three-dimensional viewing effect, whereas roof prism binoculars are more compact and lighter, but are usually more expensive due to the more complicated manufacturing process.