EN standard verified ( EN 13138 - 1: Buoyant aids for swimming instruction) , offer buoyance to user max to 60 lbs. Specific optimize [ shoulder to shoulder size ] based on "US children's body measurement data" , to match 1 - 4 years old [ shoulder to shoulder ] size, which can make kids from 1 - 4 years can wear our arm wings more comfortable and free movement. Also based on the " US children's body measurement data ", most of US 1 - 4 years old kids weight range from " 22 - 42 pounds "   ------------------- BEST AGE RANGE :        1 - 4 YEARS BEST WEIGHT RANGE :     25 - 40 POUNDS     ------------------- Original Design for kids Strengthen Construction : all connection parts reinforced by addition sewing to make it durable Additional 6 months guarantee : We offer additional 6 months guarantee, even if the time over AMZ's return time limit. Just contact us by mail to exchange a new one or others. We wil response in 24 hours.OUR MISSION: To provice the best design and product for kids, focus on product quality itself and the kid's design, save every penny for you, so we don't waste money on package.//  We are youth. We are creative. We are care about the kid's feeling. Please try and give us your real feeling. //Correction: Our printing instruction mentioned " USER WEIGHT :30 - 51 lbs", it was a mistake as we consider it's a typical US range weight, anyway, it's not the best instruction of our vest, we will make running change in future production.