i was originally looking into getting tein's flex model but have recently discovered the HA. What are the difference's between the two?

 

Well, the major difference is that they still make the Flex, the HA is discontinued for the FD, at least in the US.

The HA does not have independent ride-height adjustment and spring perches like the Flex does. The Flex also has better materials/finishes to resist corrosion better. Other than that, same springs, same shocks and valving.

 

I have the HA and each shock has ride height/spring perch adjustment at the bottom end of the spring.... is this what you're talking about? Or are you saying that on the Flex, you can adjust the ride heigh without changing the installed spring height? (without squishing or unsquishing the spring)

 

Correct, "higher-end" coilovers like the Flex can adjust ride-height without changing the suspension stroke.