Sundance Spas 2.7kW Heater with Plastic Body used in many Sundance (and other brands) spas from 2000. The heater element itself is sealed inside the unit and no other replacement parts are available for it. Also replaces Sundance P/N 6500-315 and manufacturers p/n C3403-1.

Can be used to retrofit earlier SD6500-303 cylindrical vertical stainless steel heaters used from 1995-2000 - simply requires 3 holes drilled for mounting bolts and current collector rod. 
See image with dimensions of mounting points.

NB When installing these heaters into spas manufactured prior to April 2007, sometimes you can no longer use the OEM Hi-Limit Sensor since it may be too large to fit into the new heaters sensor well. Do not force a hi-limit sensor into or drill out a sensor well. You may need to replace both the Smart Heater and sensor which have an OD of 6mm

Dimensions & Specifications:
Height: 105mm (excludes barbs)
Body Length: 380mm (excludes barbs)
Width: 88mm 
Plumbing Connection: 3/4" (the barb is connected to the hose with a metal clip)
Includes high limit thermo-disc 
Mounting bolts are 127mm apart.
kW: 2.7 / 2700W
Amps:10.5/11.5 A
Volts: 220-240
Hz: 50