Used for instant mounting and removal of Penn Fathom-Master® using your existing flush mount rod holder. Both models fit Fathom-Master® fixed base and Swivel-Matic® base. Quick Mount Jr. fits the smaller standard size boat rod holders while Quick Mount Sr. fits larger rod holders. Constructed of heavy-duty black anodized aluminum. Adapters are designed for deep trolling with downrigger boom directly astern only. However, the ReadyRigger® 662 can be used in any fishing position with Quick Mount Sr.