Durable. Unbreakable. Multi-Purpose. Safe. These rings aren't just for checklists anymore! Opaque nylon ring to hold your checklists and in-flight guides on our Fly Boys Kneeboards (with eyelets). Or use them for outdoor use where metal rings would rust or wear out. The days of the metal ring are over. Here is why. Featuring a patented ball-lock design (photo inset) to prevent FOD out on the flight line. This is not hinged. There is very little resistance to checklist pages when they move over this closure. The nylon ring is very low resistance as well. Pages really slide well, getting you to the page you want without the problems metal rings used to give.