RAM Composite Fishfinder Mount for Humminbird Devices (RAP-B-107U) (sku 54648)The RAP B 107U consists of a composite 2. 5" diameter round base with the universal AMPs hole pattern, composite double socket arm and connecting Humminbird Apelco marine adapter base. The mount is designed with a RAM 1" diameter patented rubber ball and socket system that has adjustment points at both ends of the double socket arm; thus allowing for almost infinite adjustment and perfect viewing angles. SOCKET TO SOCKET LENGTH 3" HOLE PATTERN 4 Hole