Fishhook cactus is a common name for any hook-spined species of the genera Mammillaria, Echinomastus, Sclerocactus, or Cochemiea. They are small cacti, usually growing up to 6-7 inches (20 cm) high, and are shaped similar to a barrel cactus. They are not to be confused with the fishhook barrel cactus of the Sonoran and Chihuahuan Deserts. The Fishhook cactus is a large category of around 150 species.