Post Box Wind Protector for 10mm Cable

I need to keep a cable through the post box but during winter a lot of cold air goes into the house so I made this wind shield/protector for my post box 217mm width and 38.2 mm height.My post box enlarges on the inner side so I used that to prevent the windshield to fall outside and to keep the windshield to fall inside I created arms which hold onto the outside of the post box with a length of 46.5mm.This has reduced the cold air coming through the post box significantly for me. An improved arm mechanism is in plans so that is is less likely to pop out when putting it in and out.