Serious Fly Tyers love Renzetti Bobbins. The Ruby Tip with center hole will never cut your thread, even when spinning deer hair. The Round Delrin thread pads are the same material that fine reel manufacturers use for their drag. This bobbin functions very smoothly! The black sheath covers all the snaggy parts of the necessary solder joints keeping the bobbin from accidentally getting hung on stray hackle or fibers. Midge Bobbins are smaller diameter with a standard tube length. SW (Saltwater) bobbins have a larger diameter tube and longer shaft. SW Midge bobbins have a longer, thinner tube. There is also a lead wire & tinsel bobbin without the ruby tip. Use this bobbin with spools of lead, tungsten, wire, or tinsel materials only.