honestly.... does size matter???

yep. i use small ones. though i do own this one gigantic one that my best friend got for my bachelorette party. it's un-necessarily large. but dave enjoys trying to cram it in from time to time.

 

My experience suggests that it does matter. Didn't have many girls though. But they liked it more when I made my 'friend' bigger.

 

Average = 5 3/4 inches.