The UM6080 was designed primarily as an adapter for mounting downriggers. The UM6080 was designed primarily as an adapter for mounting downriggers. When your downrigger is not in use, you can use that mount location for another boating accessory like a flush mount rod holder or a flag. The UM6080 is equally useful as a BBQ, bait board, or other custom adapter. The 4-hole pattern is a 2.5" square with ¼-20" threaded holes. Downriggers will need the addition of Burnewiin adapter plates. The UM6080 is NOT compatible with the GM400 Mount.