Loon Rigging Foams are foam discs which allow anglers to rig flies with the tippet already attached to the fly. Loon Rigging Foams are great for pre-rigging hopper/dropper rigs and keeping them ready for quick changes on the water. They are sized with the same diameter as most tippet spools so they can easily be stored on a tippet spool holder. Here is what Loon has to say about their Loon Rigging Foams: For rigging when you're at home so you can fish while you're on the water Sturdy, reusable housing for rigs using multiple nymphs, dry dropper set ups, or a single dry on a leader, allowing for pre-rigging and quick changes on the water. Directions: Rig fly or flies as desired. Insert hook into foam then wrap leader/tippet around Rigging Foam. 3-pack. Three Rigging Foams included in each package Stores rigged flies and tippet Allows for quick fly changes Minimizes waste Identical size to common tippet spools