Davis Instruments f/Windex 15 J-Base. This awesome Tool from the fine people at Davis Instruments is used to add stability to the front of the boat which allows the 'tip' of the radar to see better into the wind. The Davis Instruments J-Base f/Windex 15 comes with two #10 (5 mm) self-tapping screws drill a pilot hole in mast apply silicone sealant or Locktite and screw into mast. For a good way to make sure you are working with one of the best sailboat radar systems the sailing community has to offer choose the Davis Instruments J-Base f/Windex 15. Specifications for Davis Instruments J-Base f/Windex 15: Manufacturer: Davis Instruments Color: Black Package Contents: Davis Instruments J-Base f/Windex 15 Davis Instruments 3155: f/Windex 15 J-Base