You can't beat the quality of this field-tested circle cutter for your ceiling tile, drywall, or other material circle-marking needs. We use this tool everyday and we know it works! Long-lasting heat-treated cutting blade will give you precise cuts over and over again. Knob features grip edges, so you won't have to fuss with a slippery surface. Dial in from 1" to 16" circles. (40-400mm featured on other side) Turn the cutter over and the multi-purpose knob works as an instant hammer to help pop those circles right out! You should note that this tool is intended for marking and you will need a jab saw to completly cut through thicker materials.