The Orvis Clearwater Large Arbor Cassette Spare Spool is a replacement for your Clearwater Large Arbor Cassette fly reel. The cassette style spool allows you to replace the spool on the reel quickly and effectively to go from a floating line to an intermediate line. To change spools on your reel, there is a small, silver button located on the side of the centre screw cap. Gently press this button and pull and your spool will release with minimal effort. To replace, simply push the spool back onto the reel half until you hear a click and it will be secured in place, ready to use.