Girth Does It!
When it comes to one-night stands, girth is what does it for the ladies. They tested this by showing women a variety of dildos that "...ranged in size from 4 inches long and 2.5 inches in circumference to 8.5 inches long and 7 inches in circumference." Just for reference, that's 1/4" of an inch thick to 2-1/4" thick -- for comparison, a Coke can is about 2-1/2" diameter and 5" tall, so the "big" end of the scale is about the equivalent of two beercans stacked on top of each other. Eh, maybe they couldn't find the model of my penis and that's the next biggest dildo they could find.
Anyhow, the study found that, while women would prefer the Coke-can diameter, just one is plenty, thankuvrymuch: they'd rather be stretched, putting pressure on the clitoris and g-spot, than have their cervix pummeled by someone too long. The study also found that women overestimated the size of penises they'd seen, so stop worrying about size, guys; she's adding inches completely in her head.
Pic via.