The spare spool for Guideline Vosso Glossy Slate Black fly reel is in sizes #68, #79, #911 and #1113.
With these spare spools you are able to change different types of fly lines very flexibly and quickly without having to replace the whole reel, which is heavier and more expensive than a spare spool!
So with one rod you can fish with floating line for dry flies, nymphs and wet flies and in a few seconds you can change the spool with sinking line and rearm for streamer fishing for example and still have the same reel attached to the rod.
The spare spool are a very practical and cost-effective way to cover more fishing situations that you can encounter while during a day on the water!