Thought I would show how I packed a McCauley 6174 18" ultra sub. This thing is huge and comes in close to 40 pounds before boxing. I started with a 350 pound double wall box. I lined the bottom with 2 inches of high density foam. I bolted the driver to a piece of 1/2 inch plywood using 1/4" bolts and star nuts. It is held in place with styrafoam corner blocks. These are held in place with 1 inch foam sheets. Then I added 2 inch block to keep the entire piece from lifting off the bottom. I cut some 2 inch foam to fit around the magnet assembly and filled it with three more pieces of 2 inch foam. This thing is bullet proof now. I know it's serious overkill but new this driver was $800. I sold this one on Ebay for $410.