TomaszWI had this concern as well and I can confirm that they do fit costar stabilized switches. I have had other sets of similar thickness that did not fit. Upon closer inspection I actually found that Vortex designed these with a small lip on the inside-front of the keycap to avoid any rubbing from the stabilizer bar. It's the little things like this that make me respect a company.
I posted a pic here on geekhack showing this if you're curious.
https://geekhack.org/index.php?topic=65686.0
PacwageoThe keycap you took a photo of was cherry profile, right?
Do you know if OEM profile keycaps fit Costar stabilized switches as well? I mean, they should but who knows...
I would use those keycaps with Filco MJ2, so in theory I should go for OEM profile.
TomaszWThe keycap set I got was cherry profile. I can't say for sure if the OEM set is made with the same inner lip but I can't imagine it wouldn't be. AFAIK the only differences in OEM and Cherry profile is the overall height of the keycaps.