I think may have been 16 but not sure. I know it was on the smaller size so I'm pretty sure it wasn't a 24 seater.  It was several years ago. I do remember that for the Reykjanes tour there were only 6 of us and we all were very prompt. As a result we had so much extra time the driver took us to show us his Boy Scout Camp. I'm sure the tour company could confirm the bus size and they may have various sizes available. Enjoy your trip!
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