These ULTIMAT connectible mat joiners let you link compatible ULTIMAT cutting mats into a larger work surface for rotary cutting and expand the grid area as needed. The 9-piece set includes four corner pieces, four twin joiners, and one center cross joiner to create flexible layouts and square connections. Use them with ULTIMAT 12 x 18, 18 x 24, and 24 x 36 in mats, then disconnect the pieces for compact storage.