Hocosa of Switzerland Big Girls Organic Wool-Silk Long-Sleeve Underwear Shirt 70/30 blend of soothingly soft European KbT- certified organic merino wool & silk. Wool for warmth. Silk for strength. For Boys or Girls. Natural fibers breathe, maintaining a comfortable temperature in warmth or cold. Light-weight. Comfortable under clothing or worn alone. Wicks moisture away from skin, keeping your child dry, warm & comfortable. Even when wet, feels warm. Natural wool with lanolin gives self-cleansing properties, minimizing need for washing. Can go weeks without washing, even with daily wear. For best results, wash by hand with lanolin-replenishing woolwash to maintain hygienic effects. For best fit - European size correlates to child's height in centimeters. Choose size based on your child's height. (Ht in inches x 2.5) See Product Description below for further details.