Humminbird Knobs (Tamper Proof Bolts) Solix / Helix Fish finder Theft Deterrent Gimbal Mount.Theft Deterrent, Tamper resistance Gimbal Mounting Bolts (Replaces Existing 2 Knobs) for all Humminbird Onix, Helix , Solix Series  products, Apex 13 and 16 Models. Package Includes 2 Bolts, Two Large Black Washers, 2 Black Plastic Hinged Cap Covers and 1 Drive Bit / Key (Commercially Available) for tightening bolts. You must use your own rubber washers from your existing knobs. ** This is not a lock or theft proof product ** It is designed to keep honest people honest and deter easy removal of Control Head Units. I was looking for an Alternative to buying Locks that are made of plastic and costly. Use at your own Risk!! Tight Lines!!   Thank You!Helix 7, Helix 8, Helix 9, Helix 10, Helix 12, Solix 10, Solix 12, Solix 15