They don't recommend the herpstat intro for racks because it doesn't have a pulse proportional heating mode like many other herpstat models. Some racks that are made from metal need a thermostat to have pulse proportional heating mode so they don't produce a buzzing noise and because they don't have grounded plugs.. If your rack isn't metal the herpstat intro will do fine. Personally I would go with the herpstat intro + because it has an extra layer of safety. If something goes wrong on the herpstat intro plus it has a device that will physically cut power to the thermostat to prevent cooking your snake. The herpstat 1, 2, & 4 also have this. The herpstat intro and herpstat basic do not.