This liner was sent to me in 2020 due to a slight manufacturing defect on the first pair I bought from Sven (the founder/inventor who created Zipfit). I had already molded and skiied the first pair, so I just kept these around in a box for the last 5 years.
This model is no longer made, which is a shame, because it rips! The "Sidewinder" models feature a stiffer, more built up medial (inside) layering of material (2nd photo shows this). These also feature leather lined ankle/heel zones, which offers amazing heel hold compared to the neoprene in current Freeride and Gara models. I believe "Stealth" refers to the use of neoprene on the tongue, which just makes it easier to get into the liner.
These come with the most cork preloaded into the tongue/heel/ankle bladders, so it's either suitable for a low volume foot, or a larger shell/HV/MV boot. That being said, I made my other pair of these work in a Tecnica Cochise with a 98mm last—they completely locked me into my boots with no need for additional cork to be added, though the first several days were quite a tight fit.
If you have found these, you've likely read up on them at least a little—the differences between models can be confusing, but know that these sidewinder ones are considered to have been Sven Coomer's "Magnum Opus." The medial reinforcements stiffen this liner substantially, and make for incredible power transfer from edge to edge. I have some other Zipfit models that don't feel anywhere near as powerful/locked in as these.