The height & depth of the bulkhead will be dependent on the air-conditioning system you select. To give you a rough idea this bulkhead is approximatelty 350mm high x 900mm deep.

Thank you very much Josephine for your quick response. The unit we are looking at is 200mm high x 620 deep x 1100 wide. Do you think we would need 350 height to accommodate this size unit. Thanks. Valerie