10x40 means ten power with 40mm objective lense diameter. Go ahead and spend the money for a really good pair if you plan on using them regularly. I have spent enough money over the years on bargain stuff to buy two or three good glasses. I finally broke down and bought a pair of Zeiss 10x40's a couple of years ago. Now I dont get headaches after glassing for three hours. I think that generally speaking you will get what you pay for in binoculars. The more you spend the better off you will be. Im sure there are exceptions, but do your homework and buy something good. You wont regret it later.