4mm and 10mm refers to the thickness of the coroplast. 4mm is approximately 3/16" thick and 10mm is approximately 3/8" thick. While all the coroplast offerings on our site are the standard 4mm kind, we can also source 10mm coroplast if needed. If so, please reach out to our Support Team to see if we can assist you with your request. Please make sure to provide as much information as possible for us to be able to get back to you quickly and with pricing if it can be done. Contact Support Team at Support@4over4.com or you can use the Custom Project page to submit your request https://www.4over4.com/custom-project.