This is a revolutionary product that every angler should own. Simply place a bug between the notches and measure from head to abdomen (do NOT include attennae, wings, or tail). Quickly identifies size of fly to tie on. Includes both Streamside and Benchside (Paper measuring gauge to determine hook size to tie speciman). Streamside is 30mil thickness (credit card thickness and size); hole punched for attaching to fly vest, UV coated to prevent scratching, waterproof, tearproof, and very durable. For more information click here!