I will second John's opinion on the Wheatley boxes. I have many types of fly boxes, but the Wheatley box with the compartments on one side and the foam sheet on the other is my favorite. When you have a compartment open, the other flies stay safe from the wind. If dropped while rigging, you only fumble/lose the flies in the open compartment.

They do have another feature that works well on streams. If dropped, they sink like a rock. Usually, making retrieval easier. This feature is not as welcome on lakes.

Dan