I installed this ozonator kit into my new AR-400 spa. I love it.  I drained and then tilted the spa up to gain access to the pump area. Then, I cut one of the clear plastic tubes and inserted the injector and mounted the ozonator as instructed on one of the white water lines. Overall it took about 2 hours including draining, installation and refilling.  

 
  

Pros: Chemical use is minimal because ozone is a much better sanitizer than either chlorine or bromine. It gives the spa a healthy smell too. Definitely recommended.
Cons: It took a while to do the installation, but worth it.  Now I don't have to add a bunch of chemicals.