The filter sizes on the Large ND bar are 1.5 inch (38mm) square. Sealed edges prevents dust from collection between the layers. The ND Bar is used in conjunction with the "Swinging Flashlight" test to detect and quantify the extent of any afferent pupillary defect (APD).
The 0.3 ND filter is most useful for uncovering a borderline pupil defect. The six filters are rated as: 0.3, 0.6, 0.9, 1.2, 1.5, and 1.8 log unit optical density values. The product is 10 inches (25.4 cm) long and 2 inches (5.0 cm) wide. It is made of high grade, optically clear plastic. Comes in a pouch.
Do not use alcohol to clean this product! Use only mild soap and water.