Race fit (or "second skin") cycling pants are the tightest option available, designed with zero excess fabric for maximum aerodynamics and muscle compression. They're built specifically for competitive road cycling—think road races, time trials, and criteriums—where every watt of aerodynamic drag matters.
The trade-off is comfort off the bike. Race fit pants feel restrictive when you're standing or walking, and the unforgiving cut highlights your body shape. They're tailored for your on-bike position only, so they may feel oddly tight in everyday postures.
Don't buy race fit if you're doing casual rides, commuting, or long endurance events where comfort trumps speed. Also, avoid the common mistake of sizing up to make race pants feel less revealing—excess fabric causes chafing and defeats the aerodynamic purpose. If you want performance without the squeeze, club fit is a better all-around choice for most riders.