500R is not the greatest: the only thing going for it is the price (20-35 typically, Dr dell). The dial is a 'turn and guess' type with a little colored sticker as a guide. I'm using it with a rheostat on my corn snake cage because the corn won't need it's temps 'just right' like a BP. My recommendation is to get a ranco or Johnson, they have digital readout and setting memory.