Each butt is handcrafted with care; made from 100% cotton yarn and acrylic felt. These materials help absorb condensation leaving your table clean and dry.
I feel like I should point out that the only other item available in the Hooks + Balls Etsy shop is this darling little Zombie Cat Head Amigurumi.
Update: A number of people have asked about the pattern for these types of coasters. One of them is available on Ravelry.
[via Starry Night Cat]