Medium = 13-33 lbs, Large = 33-66 lbs. Secure Fit: Adjustable safety straps between the crotch and shoulders provide a double-locking fit. Two adjustable straps ensure a secure fit and easy on and off. High Quality: Made with thickened polyester fabric and double stitching, comfortable, durable, and colorfast. Unique Design: Slim, curved inner sleeves allow for easy arm movement safety buckle at the back equipped with a whistle. Learning to Swim: High-density Epe foam provides excellent buoyancy, helping to maintain float and balance, and boosting confidence. Adult supervision is always required. Weight: 0.44 lbs.