Sun T 3 AX

I turned this up on the BicycleMan website:

Like the EZ-Tadpole it has direct steering and is not stable at higher speeds but can still be a suitable trike for casual riding.

The unstable handling of the Sun Tadpole SX began with a steering redesign on the 2008 models. This 2008 “direct steering” version was quite unstable. Quality trikes with direct steering (i.e. Catrike) can handle very well, the EZ-tadpole does not. We feel the redesign was rushed and poorly done, making the EZ-Tadpole unstable at speeds over ~10-15 MPH. They have since redesigned the steering geometry and improved it somewhat. Unfortunately I don’t know an easy way to tell if a particular trike is the newer design.​

However, his comments are in reference to Sun EZ-3 SX Recumbent Tadpole Tricycle, not the AX you mentioned.

Also, are you sure about the AX being a tadpole? I see no Sun tadpole that has ever been referred to as an AX, only delta style sun trikes were ever referred to as an AX unless I'm mistaken.

I found this page on their website, that refers to an AX being a tadpole style trike.(i.e. The T3 CX and AX are performance minded tadpole trikes...), even though I still can't turn up a picture of an AX tadpole. ​

Another page on the SUN website states:

Model Designation Key
SX = Steel
CX = Cro-mo Steel
AX = Aluminum
HD = Heavy Duty​