Biggest problem I've found with lower end binocs is they lose collimation after a while, ie one optic points in a slightly different direction than the other due to a weak central hinge. Even mediocre optics are ok if they are aligned properly, I've seen some Leopoldo's that you needed to close one eye if you wanted to see anything! When you are testing them, just look thru them and twist one hand up and the other down, if the image goes funky, throw them back in the bin. A lot of the high end pocket binocs, you could just rip in half and use as monocular after a while... if you are using glasses check the pupil distance, point the binoc at a light and hold above a sheet of paper, move binoculars until the point is smallest then measure between eyepiece and paper- you want the furthest distance, it's amazing how close cheap binocs are.