Choices:
bottom of the line Kuuma, looks like a Seaward, but cheaper construction, 5 - 6 year life
Seaward - most likely what's there if it's rectangular, 10-12 year life, what Catalina used
Raritan - more expensive than Seaward, different shape and size, same life, on some Catalinas
Isotherm (or Isotemp? I keep forgetting) - different shape, super insulation, top of the line, long lasting and keeps water hotter for longer
YOU need to do the research to find best pricing. In 2013 I found a place in Seattle less expensive than anywhere else, some by $100 for a $250 item !!! and I was living in SF at the time. Shop smart.