Precision-machined, aluminum bobbin spools fit the Norvise Bobbin. Many fly tiers using a variety of working threads find it economical to simply change spools rather than have a separate bobbin for each thread. These spools hold from 50 to 500 yards of thread, depending on its size (diameter). It’s best not to overfill them. These bobbin spools are identical to those included in the Norvise Bobbin Kit. 10 Spools per package.