A thermal suit distinguishes itself from separate thermal pants or jackets by being one integral suit. In other words, nothing (water, wind, cold, heat ...) can get in through the traditional openings around the waist. A one-piece thermal suit has no overlap between shirt and pants.
A thermal suit must/may have a tight fit. Women's and men's models take this into account. Everything feels light and the technical fabrics are hygienic.
Thermal suits are ideal to be worn under race suits, although you can also wear them under any other garment. That a one-piece thermal suit would be slightly less comfortable or practical under two-piece outerwear is a purely personal consideration.
How does it work?
Perspiration is transported directly from the skin to the outside, where it can evaporate or be absorbed by your second layer of clothing.
Summer or winter?
Summer models keep the body dry and cool and focus specifically on quickly wicking away moisture . They also keep the lower body cool and fresh.
Winter thermal clothing emphasises on dryness and warmth. It is therefore better to choose a lined model with an insulating effect, possibly with a water repellent outer fabric. Certain models are also equipped with a windproof membrane on the most sensitive parts of the body, which ensures a pleasant feeling in cold (riding) conditions.
Tip from the RAD house
For winter, don't choose based on the thickness of the material, but based on the properties of the material.