This is a bit holder for cheap electric screwdriver from aliexpress. It is supposed to hold all the bits that come with the screw driver (except maybe one). Each bit shaft features an embedded small neodymium magnet on the shaft bottom, that has to be glued into the holder with some epoxy. 3x1 mm magnets were used in this design, though it is easy to modify the design for other magnets. The holder itself is held on the screwdriver by friction.

This item with its source file is also available in fusion360 gallery