These 2 (50mm) scales are printed with inch markings on one edge and metric markings along the opposite edge. For photos on horizontal surfaces, just lay the scale in the scene. For vertical surfaces such as bullet holes or blood spatter on walls, peel the backing off and adhere the ruler to the surface. These scales have non-permanent adhesive so they can be easily removed from evidence without damage. Scales are individually cut and packaged in quantities of 50.