We'd first want to clarify that the dimensions don't determine how many items you can send in, as you pay up front for a pre-numbered amount of items to be converted.
Additionally, you don't necessarily have to use our box! If you have too many items to fit in our box, or it's too big for the few items that you have, you are welcome to use another box. The most important thing is that you use our shipping label, barcode labels, and send everything in one box.
In regards to the dimensions, our 2 Item Starter box is: 9.5" x 10.5" x 5.5"
Our other three boxes (10 Item Family, 20 Item Closet, and 40 Item Trunk) are: 17.5" x 12" x 6.5"