I always double box the larger rare pieces . For an inner box as shown, I also use a stiff double or triple walled box big enough to tallow for at least two or three layers of padding between the outer and inner boxes. Here you see an insulator being firmly packed and embedded in large chunks of cut up recycled packing styrofoam that will not move or shift during shipment. When I close the inner box, I have arranged the styrofoam so that all the material inside is compressed a bit and tightly packed so that absolutely no shifting of the insulator or packing material can occur under any circumstances including the accidental dropping of the box . After inserting the main blocks of foam material I use little broken chunks, bits of bubble wrap, peanuts, paper wads etc as filler. This keeps the bigger blocks in place . There should be at least two inches of total material between the insulator and the outer box on all sides ... the more the better . I DO NOT use wadded paper, Foam peanuts, Puffed air bags or large bubble bubble wrap unless it is just for filler not cushining the insulator itself .I use it where it can only act to hold other more important packing material in compression . . it is not effective and useless for directly packing dense heavy things like insulators in most situations PLEASE avoid these materials !