The original heater tube fitted to Hot Spring Solana Spa Power 600 series controllers had flanged (with nuts) ends rather than male-thread. The flanged tube / heater element assembly is discontinued, and are no longer manufactured or available.
Replaced by new style with male threads on the ends of the tube, coupled with 2 supplied threaded union assemblies. This will require replumbing to suit.
It comes with the inline temperature sensor which is not actually used in Hot Spring Spas because they use an 'in-pool' sensor instead.
Note that the new style Heater will not work in spas that use a Laing ITT E-10 style pump. If you have a small E10 pump, you will need to change the whole control system.