Slim waterproof fly boxes come in four different sizes to fit your style. The large box has two magnetic compartments and five rows of foam slits. There are two options in the medium sized box. The first is a 103 Slit foam box that would be great for nymphs and midges, and the second is the 8 compartment box which would be great for midges and dries! NEW!! XL waterproof slim box with slit foam. Same design as our slim waterproof boxes now larger and with added depth to handle larger flies and streamers. 9.5 x 5 x 1.1"