Airmar 175WR-4 Transducer Housing Wrench [175WR-4]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