You'll need:-

2x 8x3mm magnets

2x M3x12 or similar screw for the back spinner.

To Assemble:

1. The fit is snug and therefor you need to run a sharp pointed object along the points of the hex pockets to sharper the corners. once this is done the bits should slid in and out easily. It best to do this before gluing
2. Insert the magnet and press in all the way, test for the click when the bit hits the magnet.
3. Use CA glue for the front tip, the sleeve and and back. place in a vice to keep all parts together for a few minutes.
4. Once the glue has set, use the screw to fit the spinner on the back, I screw mine till the can't turn then back off 1/2 turn.
5. Use a piece of filament as the hinge pin for the lid.

The sleeve can be printed in TPU, I just used the same plastic as the body for mine.

Note: This designed for ¼" bits 25mm long and 4mm bits 27mm long.