Crime Scene Documentation, Photo Scales and Rulers - Photo Evidence Rulers, Scales and ID Cards Alternating black and white 1mm bars permit measurements to be taken under exposed photographs The Bureau Reference Scale 2-piece set contains an L-shaped scale which is 300 mm long on the long arm and 150 mm on the short arm, and a second straight scale... Alternating black and white 1mm bars permit measurements to be taken under exposed photographs Circles with crosshairs are printed on each corner to assist in correcting parallax Circles with crosshairs are printed on each corner to assist in correcting parallax. OPTION: 450 x 180 mm Folding 450 x 180 mm Right Angle 300 x 150 mm Folding 300 x 150 mm Right Angle Reversible L-Shaped Reference Scales(Black White), Photo Evidence PVC Rulers, Crime Scene Forensic Supply, 5pcs/Pack (300 x 150 mm, Right Angle) L Shaped Ruler Evidence Marking, Flags - Crime Scene Forensic Supply Store Evidence Markers Excellent for scientific photography in most lighting conditions