Opteka Medium 5 X 4 inches Color and White Balance Reference Grey Card Set With Quick Release Neck Strap for Digital Photography Includes three color calibrated reference cards Dimensions 5" X 4" 0.1" (130mm by 100mm) Logo label with focus target is affixed to one side of the grey card. Both sides of the cards are usable for white balance Works with any digital camera, for JPEG and RAW files Lanyard Strap Included