The Sub-Troll 900 tells you the exact speed of your lure and the water temperature at its running depth. The ST-900 consists of only three interacting parts: the display readout, the antenna and the sending unit. The sending unit attaches to the downrigger cable, and the display unit may be installed up to 25 ft. from the downrigger. Easy to install, does not require transducers or grounding rods. It also has an illuminated display screen. Made in USA.