Swivels can cause other problems. Bright silver or brass swivels attract the unwelcome attention of toothy critters in both fresh and salt water. So I opt for black swivels. I also try to help swivels by pinching spinner blades to ensure opposite rotations and by rigging worms and such so they track unless I'm deliberately seeking a spinning effect. Then too, no swivel will eliminate line twist entirely, so it's wise to know you can unkink lines by streaming them sans lure over the side of a moving boat or into a stream.
Sizing Swivels
Common sense dictates that even the smallest swivels are stronger than your line, so use the smallest possible swivel. Many bearing surfaces are better than a couple, so opt for ball-bearings where possible. Cheap swivels with "slider or pinhead bearings" don't work well. Chain types that compound pinhead bearings are a bit better. Non-corroding materials suit saltwater. But you need not take anyone's word on all this. I didn't. I compared a decent selection of different swivels in a series of tests I picked up from Gary Soucie's expectional book, Hook, Line & Sinker.
Since a confusion of sizes and brands of slider bearing "barrel" swivels precludes individual tests, I compared common sliders with Sampo and Berkeley ball bearing swivels. I usually use Sampos (which are dozens of times more efficient than most sliders and seemingly better than other ball bearing types) where a split ring or snap won't do the job, as is the case when attaching sinkers or using bobber stops. Berkeleys are in the same class. Both use ball bearings.
Some slider bearing swivels use twist heads made from single wire. Others use split wire heads. Split heads tested better. Box-swivels use an open box body instead of a hollow tube. These were better than split head and they help you clean bearing surfaces, but spin worse than twisted head swivels. Pin head "slider bearings" common on three-way swivels were least efficient. Use cross-line bead chain types, or the Abe n' Al trolling swivel popular on the West Coast, instead.
