1.the first layer is EPE,covering the whole unit,protecting it from scratches,alleviating impact. 2.the second layer is 20mm styrofoam,density is 12.Cover the unit from 6 sides. 3.the third layer is paper angle bead.All edges are in protection. 4.the forth layer is 5-layer corrugated board. 5.last,tie up with nylon rope.