Why are there different types of spools?

There are different types of baitcast spools due to the wide variety of reels. Wide "U"-shaped spools are used when large capacities of heavy monofilament are used for bigger fish. "V"-shaped spools are designed to allow line to flow more freely during casts, helping to reduce backlash. Finally, a "shallow" spool is used when lighter line is needed for casting into shallow, clear waters.