Micro ring swivels are perfect for use with the 'claw rig'. They are also ideal for use with D-rigs. They offer better hooking qualities than a solid ring because it allows the hook bait to spin; this stops the rotation of the hook bait preventing the hook from turning inwards and catching hold in the fish's mouth as easily.
If you think about the bait and hook in the fishes mouth, as the hook link is tightened the bait will be dragged a little before the hook catches hold. If it is attached to a solid ring the hook will stop turning into the flesh when the solid ring stops swiveling against the D of the D rig. A micro rig swivel on the other hand will not stop the hook turning in because it does not stop the hook turning at all.

We tie a small hair on one end of the swivel so that the bait is actually pulled onto the barrel of the swivel so only the bottom of the barrel and the bottom eye, which slides on the D or shank of the hook, is exposed, very crafty!