Small or Large

Last night my wife and I went out to dinner. As we were waiting for some friends, we sat at the bar and ordered two sodas. The bartender poured up the two sodas and then moved on to another customer. While perusing the menu I noticed that the sodas came in a small or a large size. I assumed we got the small because I figured it would be presumptuous of the bartender to assume we wanted the large. After a few seconds we noticed that our friends were already sitting at a table. Since the bartender wasn't around, I threw down $4 which covered the two $1.60 sodas plus a tip. During dinner my wife got a refill on her soda and when it came back I noticed it was in a smaller glass. I started to get worried that I may have shortchanged the bartender because he gave us large sodas instead of small. At the end I figured I was still safe but I was a little miffed that the bartender would automatically give us a large without asking first. I would assume that if someone ordered a soda, you would give them the regular size which in this case probably was the small.

The other thing that didn't make sense is they had two different prices for refills based off of whether you had a small or a large soda. Why not just have one size of soda with one price for refills - or go free refills as many establishments have?