Well, I can't speak from experience, but I know that DW wore size 40 for years, but just got measured properly and turns out to be 44 (she'd do me an injury if she knew I was revealing that...). She is, however, much more comfortable than she has been in years.

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My dick may sound bigger in metric, but its still average. That okay, its not as if I can wear it down anyway, not that I haven't tried...