Mid-Sized binoculars usually have objective lenses of between 30 and 36mm in diameter.

For many they are the ideal compromise between light gathering potential and size:- Small enough to easily carry around and fit in with your hand luggage if you are going traveling like on safari, yet they still have large enough objective lenses to gather enough light to work well in poor light conditions, like what you often find early mornings and late afternoons when many birds and other wildlife is most active.

Reviews of Mid-Size Binoculars