Medium, but fits like a small or even an xs. I’m a 25/6 waist and 30C chest. They fit perfectly, just a touch low cut for me. Only worn twice. Tank details from their website: GOTS Certified Organic Stretch Racer Tank. Cropped tank featuring a built-in shelf bra, made for low impact activity. 92% Organic Cotton and only 8% Spandex. If you are between cup sizes or prefer some room in your band, we recommend sizing up. Short details from their website: GOTS Certified Organic Stretch Biker Short. Bike short made for low impact activity. 6.75" inseam. 92% Organic Cotton and only 8% Spandex. From a smoke, pet and fragrance free home. Please ask questions prior to purchasing. It’s important to me you have a positive experience. If anything doesn’t align, please reach out before leaving a review. Mahalo.