The Zilla Bearded Dragon Habitat Accessory Kit is ideal for 20L 60BR terrariums.
Included in Kit:

2 reflector domes 8.5 inches
Reflector dome 5.5 inches
3 dome spring clips
Day bulb 150W, Nigh black bulb 50W, Coil desert bulb 20W
Humidity and temp gauge
Terrarium liner (40BR size)
Omnivore munchies
Durable dish gray medium
Setup guide

*Enclosure sold separately*