I designed this protective box so that I could swap out the BMK band burner and battery into a different model. Also, the box protects the battery from the thrashing rubber motor. Simply install in a 1-1/32" x 5/8" hole in the model and mount on the model with screws or pegs or glue.
The burner board is held captive by some pegs and notches in the box and then retained by a dental band. You could also use an adhesive to glue the board to the box, if you like.
It weights 1.1 grams and is large enough for either the 50mAh or 100mAh battery. It is printed in ABS plastic.
