The Zoo Med Day & Night Reptile Bulb Combo Pack contains two separate bulbs. The blue daylight gives off heat for reptile and amphibian terrariums, as well as UVA which stimulates regular feeding behaviors in reptiles which should only be left on 10-12 hours per day. The red nightlight also gives off heat over a span of 24 hours for reptiles, amphibians, birds and small animals. You may choose to leave this on during the day along with the daylight if an additional heat source is required. The red bulb allows you to view your pets at night without disturbing their nocturnal or crepuscular natural instincts. Each bulb is 60 watts which are created with true red/blue glass with out the use of paints for enhanced heat transfer and quality.