What does the blue inner heat-reflective layer do?

The blue inner layer is a heat-reflective material applied to the inside of the shirt. It reflects body heat back toward the skin rather than allowing it to dissipate through the fabric, creating a higher sustained temperature against the torso. This directly increases perspiration rate during exercise, accelerating water weight loss. It is the same reflective technology used across RDX's sauna vest and shorts range.

Is this for weight cutting, or is it effective for long-term fat loss?

The M1 Sweat T-Shirt is primarily designed for temporary water weight management — the same method used by combat sports athletes before weigh-ins. Weight lost through sweating is water weight, which is rapidly replaced when you rehydrate. For long-term fat loss, the shirt may add a modest additional calorie burn during workouts, but it is not a substitute for diet and training. Use it responsibly as part of a structured weight management plan.

Can I wear it under regular clothes?

Yes — the slim, lightweight construction is designed to be worn under regular clothes without a visible bulk profile. This is useful for passive heat retention during daily activity. The water-resistant outer prevents sweat from showing through outer garments.

What size should I order?

The M1 runs M–3XL. Measure your chest (around the widest part): M fits 38–40"; L fits 40–42"; XL fits 42–44"; 2XL fits 44–46"; 3XL fits 46–48". The compression fit is intentionally close — if you are between sizes, go up for comfort during exercise. Medium is also recommended for users up to 14 years old who want a compression-style sauna shirt.