Kayak/SUP Transducer Mounting Arm made of high strength composite material that will give you years of service without any corrosion Designed for kayaks and small boat use Transducer Arm telescopes from a compact 11.5 inches to 18 inches when fully extended and swivels 360 degrees This fully adjustable design includes the 415 Slip Discs that offer infinite micro position changes Includes the 438 Gear-Head Track Adapter and our 440-4 Low Profile Track Allows attachment of our Scotty Universal Sounder Mount if desired on top of the Gear-Head Track Adapter Instantly drop and lock a Fishfinder Mount or any other Scotty post-mount accessory on top of the 141 (Scotty Universal Sounder Mount and other accessories not included) Track Dimensions: 1 3/4” wide x 3/8” tall x 7” long (4” usable track) If you want to build the protable clamp on sounder mount system - You will also want these products: Scotty 449 Clamp MountAnd Scotty 439 Track Adaptor Check out this video for details on how to put it all together: Note: You will also need 3/4 inch (1/4 20) bolts (not included)