Condoms

Young girl gets a job in the chemist shop and has to sell condoms.

Chemist tells her not to worry as most of the regulars will just ask for a 310, or 320 as a code for size, so no need to be embarrased.

Next day a guy walks in and says 350. The girl panicks and goes in the back to ask what a 350 is.

Chemist says go and look if he's carrying a bucket.

She looks ,comes back and says yes.

Chemist says ok, give him 3 pounds fifty, he's the window cleaner.