These are very useful for saving money on shipping. The material used is the key for being able to roll a big check into a smaller box. The material is 1mm thick and is made out of a PVC material. It feels like plastic, but is able to bend easily. I would recommend having more than one person hold this check because it will look rigid if you have two people holding on either side of the check.
Be careful unrolling a check upon arrival because they become spring loaded in the box. We haven't had any serious injuries from spring loaded checks, but it's still something to be aware of. We put yellow caution tape to hold the check rolled up as a final warning before opening. Check out the videos on the product page at the bottom under the "video" tab to see how to "backroll" your check to make sure it stays open and flat. Keep stored flat to avoid permanent rolling.