Having a bunch of common transistors around is always great when prototyping or experimenting. This 300 pack has 15 different transistors in quantities of 20 each. These include many of the commonly used NPN and PNP transistors. Every transistor is in the TO-92 package and can be used in solderless breadboards, perfboards, etc. (just bend the legs out to fit the spacing you need!) The transistors ship in a handy storage case with 15 compartments to keep them all separated.