The ST stands for salt and troll and fits any SUP Angler paddleboard mounting kit or paddleboard accessory ports. This is our beefier rod holder, great for saltwater rods and larger freshwater rods with a thicker butt. It uses a RAM ball-bearing mount to swivel 360 degrees with up and down adjustments as well. Rod-lock ring keeps the rod totally secure and also has an adjustable back rod-butt stop in back. Keep your rods safe and secure with the Rod Holder ST!