Fully sealed.  Silt foam lined.  The slim one-sided box can fit in tight spaces and only weighs 4.3oz or your can cover all your bases with the double sided box.
 
Thin one-sided case specs:
Space for 125 flies allowing you to have the range of ammo for your day on the water
7.66” x 4” x 0.66” to fit into your pocket nice and easy
4.3oz
Double sided case specs:
6"x4"x1.875"
Weight: 6.3oz
Room for 200+ flies depending on size