If you have ever come up with either a repair or design where a part was called out as a TO-220 you may have noticed there is another option called a TO-220FP or TO-220 Full Pack.
It is not always easy determining what the difference in packages may be and rather than searching online, here is a quick reference to the difference.
In case you are wondering, the TO means transistor outline.
Both the TO-220 and the TO-220FP can often times handle the same voltages and currents. The real difference between the two packages comes down to the thickness of the tab. Here is why :
TO-220FP is a three lead JEDEC outline where a type of plastic coating covers the entire body and the metal mounting tab that is normally exposed providing electrical insulation which increases the package thermal resistance as compared to the uninsulated metal tab style.
There are a few websites that will explain in detail the dimensional differences between the two packages, but here is an example of what I found.
TO-220 : body size (excluding metal tab) 9.2mm x 9.9mm, body size (including metal tab) 15.7mm x 9.9mm, body thickness 4.5mm, metal tab thickness 1.3mm, lead length 13.1mm
TO-220FP : body size (excluding metal tab 9.2mm x 10mm, body size (including metal tab) 15.8mm x 10mm, body thickness 4.7mm, metal tab thickness 2.54mm, lead length 13.3mm
So as you can see just at a glance the body itself is slightly larger because of the additional coating, but the place where you can really tell the difference is the metal tab thickness.