Mountain Buggy Joey Storage Bag for Duet/Duo Buggy The Joey is a brilliant new clip-on tote bag for the Duet and Duo, automatically making a side-by-side stroller a viable single child solution. Two bags in one: An easy to remove, lightweight, recyclable internal tote bag that sits snug inside a tough and durable external bag. By having the Duet and Joey combination as a first time parent, you automatically have a buggy that can grow with your family-from a single to a double. Single child options: joey with carrycot/car seat, buggy seat. When the second child comes along, simply take off the Joey and attach the buggy seat and you're ready to take two.