Speaking Option 3 (salesperson-and-customer-mobile phone)

A. So what are you looking for? Something strong but flexible at the same time, I guess?

B. Yes, they can’t be brittle.

A. They mustn’t break under stress.

B. Exactly.

A. Do you use steel? That’s strong.

....(TechTalk Pre-Intermediate, Listening Script 20.1)

Tech Talk Pre-Intermediate, by Vicky Hollet and John Sydes, p.126, tapescript 20.1