The Naked Panda Duo is the design that allows any two separate carriers to become a dual-carry option. This tandem compatible design allows the option for our carriers to grow with not only your baby but with your family too! We call this our Duo; which is one buckle onbuhimo and one full buckle (any size).  You can carry two children (same age/weight or different age/weights) at a time with this option without the double shoulder straps, you will wear your full buckle on the back and the Onbuhimo will clip in to the shoulder straps of your Full Buckle to tandem.**Or you can use the carriers separately to tandem hip carry. Full Buckles and Onbuhimos come with the tandem option so if you buy a full buckle/onbuhimo today and find out you will be carrying two children in the future you can purchase the other half of your duo at any time.**Multiple ergonomic positionsBack carry, front carry, hip carry, *outward face carry (*onbuhimo & standard size full buckle only) and tandem carry (front & back or hip & hip) options provide a natural, ergonomic position best for long term, comfortable carrying that promotes healthy hip and spine development for baby.