As far as shipping on the cores. They will not fit in a Priority Mail Medium box so the box size is a bit stange. T can cut down a box but the cost for one is a bit much. Since they are light it would be more cost effective to buy say 4 sets that way the box is still not very big and is still light and the shipping cost per set is much less. I just sent out a short kit and the postage was $17.00. I would say a set of cores would be about $15.50