A simple adaptation of the conventional rolling barrel type swivel
 
Featuring one larger eye, they are known for smoother movement over lines, tubing & leaders with most rig/lead arrangements
 
The ring swivel version is a popular choice as an attachment for those making their own leads
 
Available in two types, Ring Swivel (Sizes 8 & 11) or QC Swivel (Size 8)
Supplied in packs of 10, 20 or 50