A fellow is going on a tour of a factory that produces various latex products. At the first stop, he is shown the machine that manufactures baby bottle nipples.
The machine makes a loud hiss and pop noise. "The hiss is the rubber being injected into the mold," explains the guide. "The popping sound is the needle poking a hole in the end of the nipple."
Later, the tour reaches the part of the factory where condoms are manufactured.
The machine makes a noise: 'hiss, hiss, hiss, hiss, pop!'
"Wait a minute!" says the man taking the tour, "I understand what the 'hiss, hiss,' is, but what's that 'pop' every so often?"
"Oh, it's just the same as in the baby bottle nipple machine," says the guide. "It pokes a hole in every fourth condom."
"Well, that can't be good for the condoms!" the dismayed man protests.
The tour guide grins. "Yeah, but it's great for the baby bottle nipple business!"