Superior Quality This hole saw set is made of M42 HSS high speed steel and bimetal, which gives it higher hardness ( 64HRC) and greater strength than standard hole saws, for better cutting performance, so that it can cut ceiling tiles and plasterboard smoothly. Cutout Design With its non-binding design with clean edges, this hole saw cuts easily and smoothly. And the spring on the drill bit automatically presses the disc as soon as the hole is finished. The cut is more efficient and clean The hole cutter made of sturdy and unique HSS bimetal has sharper teeth, and has four chip evacuation holes, which has more powerful ejection capacity. Allows for quick removal of cutting material and the cutting edge is smoother. Wide application This 4-hole saw blade is perfect for drilling sheet metal, drywall, plastic pipe, wood, PVC, fiberboard, grommets, recessed spotlights and for drilling holes. Features: Suitable for: drilling metal sheets, drywall, plastic pipes, wood, PVC, fibreboard, grommet holes, recessed spotlights. Material: M42 HSS and bimetal. Size: 30mm Contents: 8 bimetal hole saws. Note: 1) When the center positioning drill is drilled, you should pay attention to start drilling slowly. 2) S 'there is abnormality or unsatisfactory chip removal during the operation, you should stop working and continue working after pouring the chips. 3) When processing thickness more than 10mm, the spring on the positioning drill should be removed. Note: this does not include other things, the color is based on the first picture, and other pictures only show the effect Due to the differences between different monitors, the picture may not reflect the actual color of the item. Due to manual measurement. Please allow deviation. Thank you!