Building Blocks are the ultimate flash cards. Used alone or with conjunction with Floors That Teach rug (sold separately), these blocks are a great way to teach letter and color recognition. The rug is made of 100% nylon. The carpet meets or exceeds Class One fire ratings and CRI Indoor Air Quality Testing program Passed (Certification No. 14222878 Category IY). Life wear warranty and three Month Limited Warranty on serging. Allow a tolerance of +/- 5% on color degradation. 1" Thick. 12"L x 12" W. Includes 26 letters of the alphabet and number 1-10.