A joke has never understood what this joke means. What kind of stalk is this?

Yu-Ching Fei once said this joke, which was a bit obscene. I want to make it clear that if the landlord is a girl, please don't be angry. The implication of "an inch old outside and a new inside" is that the penis of the ex-boyfriend is very short, only one inch long, and it has never been "occupied". Speaking of which, I don't know if you can understand! :-)