The Unite 2 21" EXPANDABLE SPINNER luggage features the Link2Go in its upright spinner models. which is a innovative way to attach two Spinners together. It's easy. just connect the Spinners back-to-back with Velcro straps and you're ready to roll multiple suitcases with one hand. Amazingly versatile and lightweight. the affordable Unite 2 is perfect for family travelers who need an extra hand. Now busy families can roll more pieces. more easily. Connect luggage back-to-back and push two pieces with one hand!