This is a transducer unit for the Barnacle Buster system. We don’t have any more of the system, just what is seen in the photos. About the size of a hockey puck.
Ships free in the US, thanks for looking!

All items sold at Max Marine Electronics come as you see in the pictures provided, with ONLY the parts and accessories shown in the pictures, PLEASE do not assume any additional items will be included in your shipment. IF YOU DO NOT SEE SOMETHING YOU EXPECT TO BE INCLUDED IN THE PICTURES WE PROVIDE, IT WILL NOT BE INCLUDED. Please read all descriptions thoroughly, as there are times a display is used ONLY to show the item being sold is functional, working properly and these displays ARE NOT included and this will be stated in our descriptions. If you have ANY questions please always feel free to send an eBay message or call Max Marine Electronics Inc, Pompano Beach, Florida for help, assistance or more detailed information. We always want to be transparent with our customers and fully disclose any information regarding the products we sell.