I teach an infant/toddler sign language and music class and am always looking for new instruments...at a good price. The cheapest sand blocks I could find online were $2.80 a pair. Doesn't seem like a lot, but buying enough for all of the kids would've been too much for my budget. I saw these stamps in Marc's 5 for .99. and bought a pack of sand paper for .87. After removing the rubber stamp from the block, I hot glued sand paper to them. They sound just like the real thing and Ben had a great time playing with them!