Subal recently responded with the announcement of their 'Type 4' port mount, now shipping on housings for the Canon 40D and 1DS MKIII, as well as the Nikon D300, D3, D800.
Type 4 port mounts can be distinguished from earlier Type 3 mounts as follows:
| Type 3 | Type 4 |
|---|---|
| Housings: To determine the port type for your housing, measure the diameter of the opening in the mount. | |
| A housing with type 3 ports will measure approximately 100mm (4 inch). |
For type 4, the measurement will be approximately 110mm (4+3/8 inch). |
 |
 |
| Ports: If you don't have a Subal housing at hand to determine what ports you have, measure the external diameter of the mount lip (not the bayonet flanges). | |
| For Type 3, the measurement is 93.5 mm (3.68 in) | For Type 4, the measurement is 102.5 mm (4 in) |
 Subal Type 3 Port |
 Subal Type 4 Port |