Fast Tip for Putting Backing on Your Reel

The amount of backing I decide to use depends on the line size I'm using and what I am using it for. I'd rather be able to fill 3 or 4 spools on my reels with a 300 yard spool of line than just 2. Why waste money and line when you're only going to use maybe 60% of the line that's on there anyways....