From the manufacturer:
The Clear on Clear System makes stamping easy! Stamps and blocks are crystal clear so you can see where you are stamping. Stamps cling like magic, easy on, easy off--no adhesive and the blocks have wavy edges for a no-slip grip. Each set is themed with stamps that you can use individually or together. Create unique cards, gift wrap, tags, fun accents for scrapbooking, and more! This package contains one 2.25x1.75 inch acrylic block and one 3.5x2.5 inch acrylic block.