A classic stick on thermometer that has a large range (36°-78°F; 2.2° - 25.5°C) in 2°F increments. This particular fermometer shows both the lager and ale range so at a quick glance you know where you are. Peel off the back and stick it to your fermenter.
Adhesive is permanent so once it is stuck on do not peel it off or it may not stick on again.