Numberblocks One to Twenty are ready to help children learn early counting and number sequencing skills. Start by building a 5-piece puzzle featuring Numberblocks One to Five and gradually progress to building a 20-piece puzzle featuring Numberblocks One to Twenty. Introduce early math skills such as counting and number sequencing with your children's favorite Numberblocks One through Ten characters! Colorful, self-correcting puzzles are the perfect way to introduce counting and number sequencing. For ages 3 years and up.