Cast iron concrete cube moulds used in engineering and laboratory settings.
They are designed to create standard-sized concrete specimens for compressive strength testing and quality assurance.
These specific moulds appear to be 150mm x 150mm x 150mm in size.
They feature a heavy-duty construction with detachable sides for easy release of the cured concrete. [1, 2, 3, 4, 5, 6, 7]