3 Pen Scribers For Marking Jewels, Metal, Glass and Plastic. This is a new set of 3 pen scribers. These can be used for marking on metal, glass and plastic. Two of them are formed in a hexagonal shape to prevent it from rolling. One is reversible so the point can be protected while carrying. Each measures approximately 5 1/4" (133 mm) long. You receive: One wall scriber. One carbide tipped scriber. One diamond tipped scriber.