Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
What is the maximum diameter of the Mid West Gas Pipeline (1999)?

### Inputs:
table_name: table, columns: ['Name (year commissioned)', 'Owner/operator', 'Length', 'Maximum diameter', 'From/to', 'Licence number']

### Response:
SELECT Maximum diameter FROM table WHERE Name (year commissioned) = mid west gas pipeline (1999)