The following happened to me a few years back when we were doing up our bathroom. Hubby was in the middle of connecting copper pipes when he realised he was missing a very important piece. So, he asked me to go to the local plumbing merchant and bring back a 15mm Tee piece so he could finish his soldering.
So, when I got there, I thought I would first say the general term and then, specify the exact diameter I was after and said: “Could I have a cooper Tee, please” and before I had time to specify I wanted 15mm rather than 22mm, the guy laughed and replied: “A cup of tea?? You can come and have a cup of tea with me anytime!”…. I did feel silly but at least, he had a new story to tell his colleagues
What would you have said though if you were after the same thing yourself??