Size 64 is +/- 15% wider than the average condom size. If you have measured this size you can expect that a wider condom will roll off more easy and feels better during sexual intercourse. Also the possible loss of erection due to a too tight condom might be prevented.
Not every penis is the same and condoms can have different fits (shaped or straight). Depending on your feeling an adjoining size (smaller or larger) might feel just a bit more comfortable.
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