The benefit of using a sling pack is the added storage. With that in mind, my go-to items are fly boxes, rigging accessories, rain gear, and water. These essentials keep me ready for any situation I might encounter. The storage capacity lets me bring all my fly boxes. On the water, I can quickly change between dry fly fishing and nymphing without worrying about the boxes I'd otherwise have to leave behind. Depending on the pack, net holsters allow you to bring a net to land fish. Packing a bag with these key pieces of gear gives you a storage solution that has all your needs on the water covered.