Most of us are familiar with the Hollis M1. Here are some side by side pics.
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now the M1 looks bigger but that’s because it is farther away and the wide angle on my camera phone. As shown in the next picture the width is the same.
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The M1 is slightly taller. The skirt of the Deep 6 feels softer so I am not sure if that cancels out that it is wider as shown below (M1 on the bottom, Deep 6 on top)
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The masks are fairly equivalent in my opinion. I’ve only put in a few dives, but my Deep 6 will be my primary mask, and M1 my backup.
IMHO the M1 has the stiffest, most uncomfortable skirt of the many frameless masks I’ve used so anything will seem softer by comparison. By contrast the DGX mask is my favorite so far.