Our 100% Merino Wool Long Sleeved Top is great to wear under long sleeves, a turtle-neck, or as pajamas. Warm and soft and machine washable. A great layer of protection for playing outside during cold weather. These are children's sizes, similar to American sizes. The size is close to the age. Size 4 should fit a 4-6 year old child. Size 6 should fit a 6-8 year old, etc. Wool is from Australia, sewn in Denmark.