Box Blocks are huge and immensely strong. The largest probably require two kids to manipulate or move. They are the next scale up from standard unit blocks and typically they are used in schools and pre-schools in small numbers to allow children to build structures that are kid sized. While they are very sturdy, they are not meant to be used outside in the wet unless they have been painted or coated with some sort of preservative. They can be wiped down with disinfectant; just dry them promptly.