MJ 15024 and 15024G are G-free, which means that these two transistors are named according to Japanese standards. In fact, the number should be preceded by 2S to be its real name.

There are many models of this kind of high-power sound tube, such as MJ 15024 and MJ 15025 from Motorola, 2SC2922 and 2SA 1265438 from Sanken, 2SC5200 and 2SA 1943 from Toshiba, which are all commonly used high-power sound tubes.