I was going thru my old pics and found these and thought others may find them useful. They are small and large size cookie tins. The small ones (approx 6 inches round) work well for 1 gallon plastic waterers. The Larger one works well for the wider mouth 1 gallon waterers and 2-3 gallon waterers. I use a 25 or 40 watt bulb, depending on temps. Typically 25 watt is sufficient.
Jody
Jody