Lots of 2 closely matched pairs of BC108 NPN Silicon transistors in the TO-18 metal package. These transistors are matched up to each other within 10(Hfe). There are several sets to choose from in the pull down "select" menu. The tops of the transistors have been marked to designate which is which with an x or a •. These symbols indicate the hfe value for the particular transistor. It wipes off easily with isopropyl alcohol. These values are printed on the bag.