Marbles

A 18yr old Boy and a 18yr old girl just finished playing marbles & decide to see who won the most marbles. I have 6 red said the boy but the girl replied that she had 8. I have 9 blue said the boy but the girl said she had 11. This was repeated with the yellow and green colors and the boy was getting a bit frustrated so he dropped his trousers took out his willy and said “I bet you don't have one of these”.
The girl replied by lowering her pants and said “No! But I do have one of these and, with one of these, I can get as many of those as I want”