Minecraft Jiao Er is a energy measurement unit set for Buildcraft for its own.The English abbreviation is MJ.

Only engines (including redstone engines, steam engines, and combustion engines) that can generate MJ in Buildcraft.

Some devices in BuildCraft need to work by consuming MJ.

At present, MJ energy has been abandoned, so that many module -universal "RF" energy is used.

After 7.99, the version is changed back to MJ’s universal cable.