Compatible with both spinning and casting reels, specifically designed for rugged environments and large fishing rods. It features a rotating ring to keep your rod in place and a swing arm rod stop that can convert it into a tube style rod holder. Compatible with the C-Size and B-Size hex ball bases. Includes a 6" spline post and bulkhead/flat surface mounting base. Also GoPro compatible - just attach your GoPro factory mount directly to the rod holder or use the Double Ball Mount to attach any action camera. If you want to mount your phone to utilize your mobile fishfinder app, use the Double Ball Mount with X-Grip.