These transparent acrylic boards provide the perfect acrylic base for your mosaic projects. Place over artwork and photographs, apply adhesive, position tiles, grout, and then wait for your mosaic to dry. Congratulations! You’ve created your own mosaic masterpiece. All bases measure 1/4 in. thick. 8 in. x 8 in. and 8 1/2 in. x 11 in. bases are sold separately. 4 in. x 4 in. base comes in packs of two.