If you want to be able to quickly and easily remove your downriggers while transporting or storing your boat, Big Jon's "Quick-Slide Mounting Base" is the best solution.
It is constructed from machined aluminum to assure that it has the strength that is needed to securely mount your downriggers to your boat.
It accepts all Big Jon downriggers and rod holders with 4 in. x 4 in. bases.
The Quick-Slide Mounting Base has been treated with a black anodized finish to prevent corrosion.