Dremel's 453 sharpening stone is ideal for sharpening chain saw blades quickly and easily. There are two per pack. The bit diameter is 5/32"" (4.0mm) with 1/8"" shank. The cutting part of a chain saw blade is the top of the tooth, not inside the curved portion close to the bar. In order to sharpen the underside of the top part of the chain saw tooth, lift up on the attachment. When lifting upward during sharpening will provide a excellent cut and greater satisfaction.