How to place a 7805 voltage regulator on a breadboard?
If you look carefully at the data sheet drawings, some have wider leads than others. 

TI LM341/78M05



Fairchild LM78M05



A typical maximum diameter for a solderless breadboard is 0.91mm (AWG 19),
so the Fairchild part will be too big, whereas the TI part will probably fit fine.