You may be asking what is a MILS plate ? The simple answer is it stands for Modular Integrated Landscaping System. The system was created by a LUG (Lego User Group) to allow it's members to create MOC's (My Own Creation) to be linked together at LEGO shows. It has however been adopted by a large number of AFOL's (Adult Fans of Lego) for their city building, as it provides a much more stable base than the LEGO baseplate. Once you have tried one of these plates you won't use anything else for your baseplates.