This is an improved screen for the size 0 Lewmar opening port, old standard and new standard. This port's lens measures 4" x 10" and has paddle like dogs which flip up and down to open and close the port.
This new screen is improved in several ways:
The dimensions of the screen are:
Top to bottom: 4-1/2"
Fore & aft: 10-3/8"
For identification purposes, the dimensions of the size 0 port are:
Top to bottom: 176mm (6.93" or about 6-15/16")
Fore & aft: 323mm (12.72" or about 12-11/16").
We know from experience that this size port was occasionally used on the CP-26, the C-27, and the C-42, and there may be other boats that use it as well. Please check the dimensions of your port to confirm the size.