Dark Matter Shirts, Black Cats, Cosmic Kitty, Halloween Shirts, Great Gift for Science Teachers, Scientists, Cat Lovers, Geeks and Nerds Eureka! We finally know what dark matter is! It's the comic black cat whose presence fills the universe. This cute Halloween shirt makes a great gift for any cat lover, science teacher, scientist, astronomer, astrophysicist, space lover, geek, or nerd. About the Shirt; This crowd favorite features a crew neck, short sleeves, and a standard fit. Solid colors are made out of 100% Airlume combed and ring-spun cotton, 32 single 4.2 oz, while heather/CVC colors feature 52% Airlume combed and ring-spun cotton, 48% poly blend. Care Instructions: Machine wash and tumble dry on low. Size in inches Extra Small (XS) - 16.5" width, 27" length Small (S) - 18" width, 28" length Medium (M) - 20" width, 29" length Large (L) - 22" width, 30" length Extra Large (XL) - 24" width, 31" length XXL (2XL) - 26" width, 32" length XXXL (3XL) - 28" width, 33" length.