Some housing owners suspect the so called "mold release lines" (slightly raised areas) in the O-ring groove on the door of the housing may cause the housing to leak. Some have suggested sanding down these "mold lines" with 600 or 800 sandpaper to allow the O-ring to better seat in its groove thereby preventing any possible leakage. I am not advocating that process here but simply pointing out the locations of the "mold release lines". The lines on my G10 housing are less pronounced than those on my G12 housing. The lines on my G12 housing are indicated in the below photos.