The Wiha 40010 Magnetizer/Demagnetizer is the perfect tool for fastening screws and small parts in tight spaces. With its powerful c8 permanent industrial ceramic magnets, it magnetizes screwdriver blades quickly and easily. It works with items up to 1.35" in length and 1/8" or 3mm in diameter. Its 2 x 2 x 1.125-inch size makes it easy to use, and no batteries are ever required. Plus, it's backed by the Wiha No Hassle Guarantee.