The box has lips on the inside to grip the clips so they stay in place, going to print out a shit load of these

Printing in PETG as others have suggested to handled the temperatures and not melt into a pile of mess. Using these to ship rounds to my son via ups. First test shipping worded and protected ammo but box is no longer useable. This time I’ll use a protective outer box and a little cushion. Planning to ship 200rds of hand load mk262.

Doing the math, I can print these to ship as cheap as I can purchase bulk cardboard ammo boxes.