Complex sentence: An initial batch of 10 Kometa-Standard IIs was built, followed by two batches, each of 10, of Kometa-Standard IIIs, for use by Bulgarian clubs; they were fully aerobatic, though not cleared for cloud flying.
Split into simpler sentences: An initial batch of 10 Kometa-Standard IIs was built, followed by two batches, each of 10, of Kometa-Standard IIIs. They were fully aerobatic, though not cleared for cloud flying.