Product Description: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. - As far as Safety goes, there is no question this is the ring to use. You don't need to be trying to get 10 of your checklist pages off of the cockpit floor so you can finish your Electrical Failure checklist! Once they are closed, they stay closed. - These rings are affordably priced, considering they virtually last forever. Also, considering the cost of a jet engine is 5+ million dollars - it is the cheapest and best FOD prevention tool available! - When closed, they are a 1.5" diameter ring. Opened, they stretch to 5". For most applications 4 rings is plenty for keeping your checklists or inflight guides secure. - If your squadron doesn't have these rings for you, they should! FOD prevention is serious stuff.