Due to shortage of Rolls-Royce Merlin engines, some 300 Lancasters were built with Bristol Hercules radial engines, becoming the BII Variant. Some were also fitted with enlarged bomb-bay doors to enable large 8000lb bombs to be carried, as well as a ventral defensive turret. Features include complete Bristol Hercules engines with detailed exhausts, optional dropped flaps, ventral turret and fairing, optional retracted undercarriage and fully detailed interior.