Polar Tech's 'Nestable' foam shipper is offered as a FOAM ONLY option to allow for flexibility in it's application and for nestablity. Each foam cooler nests within each other providing more storage space and more shippers per tray. Polar Tech recommends using an outer carton for most shipments (Check with your carrier on how the boxes will be allowed to ship). Our superior quality offers durability, temperature control, and superb reliability for most shipping purposes. These products are MTO (Made to Order).