Fishhook cactus is a common name for any hook-spined species of the genera Mammillaria, Echinomastus or Sclerocactus. 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 (Ferocactus wislizenii) of the Sonoran and Chihuahuan Deserts.