This is a ring-shaped strong magnet for screwdriver head, also called bit ring magnet, neodymium-iron-boron material, N38 grade, OD 15mm, hole 7mm, height 10mm, can be set on the top of the electric batch head, the screws are not easy to fall off, it is recommended to buy 1mm bigger than the batch head when you buy, easy to disassemble.
Picture of a 15x7x10mm strong magnetic ring on an electric batch head
Close to size recommendation;