Oko Test certified sling - Free from any harmful chemicals or residue. Hoppediz is a high quality wrap-around style sling distributed from Germany. The cotton fabric is tested for chemical residue and is certified to be free from any harmful agents. Hoppediz baby slings are also available in certified 100% organic cotton. We have been very impressed with the comfort of Hoppediz slings. Hoppediz has detailed colored photo instructions which are some of the best we've seen and show special tricks for tying. Hoppediz slings have a mark at the center. To make sizing easier, Hoppediz comes in three sizes: small (2.5 meters), average (4.6 meters), and long (5.4 meters). If you have any questions or concerns about your size, please contact us!