Most children, when presented with the option between two drink items, will choose the one with "more." But what exactly do children consider when they recognize one object as having more than another? Is it the perceived surface area or volume of an object? Depending on children's cognitive development, the aspect of measurement on which they focus can differ. In an effort to encourage students to consider how mathematical ideas can be used to explore the measurement of "more" in a real-world situation, the authors presented them with a mathematical modeling task entitled You Pour, I Choose (Meyer n.d.). Twenty-one students in grades 6-8 from five schools engaged in this task at a two-week summer camp led by the second author and a teacher. They watched a video of soda being poured into two different sizes of glasses and were asked to determine which glass contained more soda. Because students began to discuss this task as a class prior to solving in groups, recognized that the discussion strategies used by the teacher were facilitating productive mathematical discourse. Specifically, students were sharing ideas, extending their thinking, clarifying their understandings, and cultivating credible argumentation (Smith, Steele, and Raith 2017), all of which support students' development of mathematical models. This article aims to describe a teacher's discussion strategies that promoted productive mathematical discourse during this mathematical modeling activity. Although authentic mathematical modeling lessons allow for the ubiquitous usage of these strategies, the authors chose to limit their strategies to the launch of the lesson to best showcase productive mathematical discourse.