Mandrels are used to mount different accessories to use with your Dremel rotary tool. The 402 Dremel Mandrel features slotted screw head and a 1/8 In. (3.2 mm) shank. The 402 mandrel is typically used to hold accessories like cutting wheels and sanding discs. The flathead end of the wrench included in most rotary tool kits can be used to loosen or tighten the screw on the mandrel when doing accessory changes.