This just in: the ratio of chihuahua to tennis ball is indeed correct!*
* [Editor's note: this statement has not been fact-checked, but if you test it out with your own chihuahua, be sure to let us know!]
Medium (Men's 3-6 Shoe / Women's 5-9 Shoe)
Large (Men's 7-12 Shoe / Women's 9+ Shoe)
Machine Wash Warm, Wash Inside Out. Do Not Bleach. Tumble Dry Low. Do Not Iron. Do Not Dry Clean.