How they compare
Exxxtra Small is TeamSkeet's petite series: about 590 scenes since 2016 with slim, small-framed 18+ performers, often paired with much bigger partners. It's $29.95 a month or $149 a year to stream, with all of TeamSkeet included.
Fit18 films slim, athletic performers in a scripted "fitness casting": a workout or flexibility test before the sex. At the time of writing it was $14.95 a month in a 50% sale or $59.95 for 180 days; the homepage doesn't date its scenes, so the update rate isn't clear.
Exxxtra Small gives you more scenes and a whole network; Fit18 is for fans of its gym-casting premise.