Slice ceramic utility replacement blades are designed to work exclusively with Slice handles (sold separately) to optimize safety and function. Compatible only with • #10550 Smarty Manual Cutter • #10554 Smarty Auto Cutter • #10558 Smarty Smart Retractable Cutter. For other Slice Boxcutters (10400/10503) or Pen cutters (10512/10513) or Craft Cutters (10514) please utilize Slice 10404 (Rounded Tip) or 10408 (Pointed Tip) blades. Both blade options feature dual sided edges. 1.3 mm thick for strength and durability. Patented blade with proprietary sharpening creates a safer blade. Double sided equivalent of up to 20 single-edge blades. Use the pointed blade tips (10528) for cutting thinner items like paper. On the Mohs hardness scale, Metal blades are rated 5.5 vs. Ceramic blades at 8.2, second only to diamonds. Harder edges maintain sharpness longer, cut better, and require replacement far less frequently. In fact, depending on use, you can go weeks or months without having to replace a single ceramic blade. They also last up to 10x longer!