This wrench is specifically designed for the salt water chlorinator system on the Hydrojet™ pumps. It is recommended you use one when undoing the electrolytic cell. Great for maintaining the Lay-Z-Spa™ Hawaii and Lay-Z-Spa™ Palm Springs Hydrojet™ models. Compatible with Lay-Z-Spa HydroJet models BW54138 BW54144 BW54173GB. NOT compatible with any other Lay-Z-Spa™ model.