This slim pocket file is convenient for storing commercially available tapered leaders, including their packaging. The back of the file features beginner-friendly illustrations of basic knots. By placing a 3-in-1 Nail Knot Pipe in the Nail Knot Pipe holder on the lid, you can quickly prepare for leader changes. The slits on the side fit a foam changer, making it extremely convenient to store in an S-size system case.