The curved handle wraps around your hand and rides along the box as you cut, so the blade travels in a straight line instead of diving in. Its edge is 100 percent zirconium oxide — a ceramic that’s cool to touch even bare-fingered — set to one of three depths, the shallowest sized for slicing packing tape without ever reaching what’s inside. Slice says the ceramic lasts 11.2 times longer than a comparable steel blade, and it never rusts.