Waterworks-Lamson Cobalt 10 Spare Spools fit the Waterworks-Lamson Cobalt 10 Fly Reel. The Waterworks-Lamson Cobalt 10 Spare Spool is perfect if you already own, or are purchasing the Waterworks-Lamson Cobalt 10 Fly Reel and want to use your reel on two different outfits, or you want a different fly line, such as a sink tip or full sinking fly line to adapt to changing fishing conditions. This product is the Spare Spool only.