I believe when the tyre was first launched the PS4S was only available in 19", 20" and 21" sizes worldwide. This appears to have changed for the USA market in February 2018 according to this article - https://michelinmedia.com/pages/blog/detail/article/c/a706/
I believe in Europe and possibly anywhere outside of the USA and maybe Australia(?) 19" sizes are as small as is available in this tyre. Maybe someone could confirm? I'd be interested to know and more interested to know why Michelin would do this if it is the case. I would have thought - USA + AUS = bigger cars with bigger wheels and therefore more demand for the larger sizes and the opposite in Europe
I'm going to get the firehawk indy500 because bang for buck. indy500 are only slighlty inferior in almost every wear except for treadwear and $$. I dont plan on being very competitive so I think these work best for me