The octopuses should be smaller than we could think. Premature babies very often lie among different tubes and equipment in small incubators which is why the octopus comforters have to be so small. The size of the octopus’s head should be 3.5-8 cm long and have a minimum diameter of 3.5 cm. Tentacles should be 10-16 cm long for octopuses with heads 3.5-5 cm long and 16-22 cm long for octopuses with heads 5-8 cm long.