It should be pointed out technique is critical when using the handheld demag devices as it is very easy to put the magnetic charge back on the disc if the button is released when the demag is too close to the disc. There is also the distance of the device from the disc to consider, 1/2 inch most likely too close. I suspect a minimum of one inch is correct. I also suspect demag of both sides of a disc might be a little excessive.