Researchers from the UK’s Durham University and Germany’s Fraunhofer Institute claim they’ve come up with the world’s first manufactured non-cuttable material, just 15 percent the density of steel, which they say could make for indestructible bike locks and lightweight armor.

The material, named Proteus, uses ceramic spheres in a cellular aluminum structure to foil angle grinders, drills and the like by creating destructive vibrations that blunt any cutting tools used against it. The researchers took inspiration from the tough, cellular skin of grapefruit and the hard, fracture-resistant aragonite shells of molluscs in their creation of the Proteus design.

An angle grinder or drill bit will cut through the outer layer of a Proteus plate, but once it reaches the embedded ceramic spheres, the fun begins with vibrations that blunt the tool’s sharp edges, and then fine particles of ceramic dust begin filling up gaps in the matrix-like structure of the metal. These cause it to become even harder the faster you grind or drill “due to interatomic forces between the ceramic grains,” and “the force and energy of the disc or the drill is turned back on itself, and it is weakened and destroyed by its own attack.”