About the size: Size: Size S fit for shoulder width: 30-38cm,weight:17.5-35KG(Children Size) Size M fit for shoulder width: 38-43cm,weight:35-60KG(Univeral Size) Size L fit for shoulder width: 43-46cm,weight:60-84KG(Adult Size) Package: 1 pc Posture Corrector belt Note:Can';t use it when sleeping. Features: 1. Corrects your posture and restores healthier stature to your body. 2. Reduce lower back pain, slouching and hunching. 3. Contribute to growing development. 4. Health products for men and women bodybuilding, for office daily wear. 5. Fully adjustable, comfortable & easy to wear. Functions: 1. Helps support, comfort & relieve aches & pains. Helps improve breathing, relax muscles and straighten neck, spine and your head. 2. Helps pull the shoulders back to stand tall & sit up straight. 3. Can be discretely worn under clothing. 4. Suitable for adults or children Hello, this correction strap is adjustable, if you feel it is tight, you can adjust it by magic sticker.