A size label is only one part of fit. Cycling apparel changes shape on the bike, across brands and across product categories, so the best decision comes from reading several clues together.
Decode fit language
Race, slim, regular and relaxed are not universal standards. Treat them as intent signals, then compare them with product measurements, fabric stretch and model notes where available.
Think about the ride position
Jerseys and jackets can feel different when standing compared with riding. A shorter front, close sleeve and firm pocket structure may make sense on the bike even if it feels unfamiliar off the bike.
Use size help before checkout
If you are between sizes, open the size guide from the product page and consider whether you plan to layer underneath. For Sale items, confirm service terms before buying.