J-Base for Windex; 10.Sport for Side, Top or Front of Mast MountingAllows for side, top, or front mounting on most masts, on big boats or dinghies alike. Standard with the Windex 10.Sport, J-Base™ can be ordered as an option for Windex 15.Standard with the Windex 10.Sport, J-Base™ can be ordered as an option for Windex 15. Allows for side, top, or front mounting on most masts, on big boats or dinghies alike. J-Base is made of glass filled polycarbonate, 2″ (5 cm) long. Includes stainless steel set screw and (2) #10 self-tapping screws. Reduces overall weight by 15 grams when substituted for standard mounting base on Windex 15.