175WR-4 Transducer Housing Wrench A single-handed wrench that holds the main thru-hull housing via the 'wrench flats' on the top of the housing to facilitate tightening of the hull nut. Use wrench 164WR-2 or 164WR-3 for the hull nut. For use with: * B164 * B175 * SS164 * SS264 IMPORTANT: the design of the housing for these transducers changed slightly in June 2012. This wrench is for the newer design and has an internal width of 2-3/4'. If you need a wrench for the older designs then use the 164WR-4 instead, with an internal width of 2-7/16'.