The H3 Launch Vehicle is an expendable launch system in development in Japan. Each H3 booster configuration has a two-digit and a letter designation that indicates the features of that configuration. The first digit represents the number of LE-9 engines on the main stage, either "2" or "3". The second digit indicates the number of SRB-3 solid rocket boosters attached to the base of the rocket, and can be "0", "2" or "4". All layouts of solid boosters are symmetrical. The letter in the end shows the length of the payload fairing, either short "S" or long "L". For example, an H3-24L has two engines, four solid rocket boosters, and a long fairing, whereas an H3-30S has three engines, no solid rocket boosters, and a short fairing.