There are five form factors for Pentium^® III, Pentium II, and Intel^® Celeron^™ processors: S.E.P., S.E.C.C., S.E.C.C.2, FC-PGA, and the PPGA form factor. These five form factors are illustrated below along with a brief explanation of how to easily identify them.

S.E.P. Form Factor
		Boxed processors in the S.E.P. form factor are not completely covered by the blackplastic shrouding like the S.E.C.C.and S.E.C.C.2 form factors are. The substrate(circuit board) is visible from the bottom side.
S.E.C.C. Form Factor
		Boxed processors in the S.E.C.C. form factor have a plastic shroud covering with an active heatsink and fan. The best way to identify this package form factor is by the goldfinger contacts - on a S.E.C.C. form factor, they are seated inside of the plastic housing.
S.E.C.C.2 Form Factor
		Like the S.E.C.C. form factor, boxed processors in the S.E.C.C.2 form factor have a plastic housing with active heatsink and fan. The most noticeable difference is that the goldfinger contacts are exposed on the S.E.C.C.2 form factor as shown in this photo.
PPGA Form Factor
		Boxed processors in the PPGA form factor are in a 370-pin socket form factor instead of the slot connector form factor. You can tell if you have a processor in the PPGA form factor by locating the Pin Grid Array on its underside. Slot connector form factors do not have pins.
FC-PGA Form Factor
		Boxed processors in the FC-PGA form factor are also in a 370-pin socket form factor instead of the slot connector form factor. You can tell if you have a processor with a FC-PGA package by locating the Pin Grid Array on its underside. Slot connector form factors do not have pins.