Design, manufacturing, and sales of building materials machinery, compound fertilizer equipment, chemical and metallurgical machinery, specialized equipment for oil drilling, power machinery, and non-standard mechanical equipment; production and sales of general steel structures; sales of standard parts, bearings, and mechanical accessories; installation, modification, and maintenance services for mechanical equipment; production and sales of vehicle parts; self-operated and agent import and export of various goods and technologies, excluding those restricted or prohibited by the state.