Size 4 Ringer Swivels are most commonly rigged with horse size ballyhoo, Spanish mackerel, and bonita when targeting blue marlin with circle hooks. The o-ring is perfectly sized to accept the industry standard 12/0 and larger circle hooks, allowing you to quickly change out baits like years past with o-rings with the added benefit of 360 degree rotation provided by the swivel. The added rotation will no doubt help you to increase your hook up ratio out in the deep!