There are many different types of UTHs available. I personally like to use flexwatt because its affordable and very reliable. The UTH should cover about 1/3 to of your snakes enclosure.

Its very important to have some sort of Thermostat or Rheostat to control the output of your UTH, without one you risk burning your snake. The belly heat that UTHs provide is very beneficial to the digestion process of your ball python.

I buy all my heating supplies from Rich at www.reptilebasics.com his customer service and shipping times are 2nd to none.