First of all, these boxes are free from the USPS website or via Ebay's postal site.  The boxes are great, but you must consider that the items that goes in the boxes, should be wrapped.

The reason for wrapping the items, is that the glue sometimes overlaps the folds at the ends of the larger boxes and will cause your item to stick, and do I mean STICK.

But, by the same token, the flaps do sometimes come apart, and do not stick and you possibly will lose the contents.  I always wrap tape twice around the whole package, to guarantee that the flaps will not come open.

The smaller boxes are notorious for this, so always tape securely.

Now, this is advice I got from my Post Office. Use mail stickers for priority mail (Free) to past over the Paypal logo, if you print from Ebay. The Post Office Supervisor said that it encourages tampering when the logo is seen.  I do not know the truth to this, but you can use it with your own design.  I personally do not cover the logo, but somehow, someone had a problem.

Everything I ship from my auctions are in a box. I even ship Corvette fobs in a box as well as numerous Corvette brochures. The boxes do protect and seem to never get lost. 

I hope I helped you with this information

Catmeow17  >^..^<