This article describes the two types of reasoning in fraction conceptions that students often use, "gap" and "missing piece," and one that the authors aspire their students to reach, "residual." Each of these types of reasoning are underpinned by a different conception of fractions. Students who use "gap reasoning" to compare fractions are guided by a whole number conception of fractions, while those using "missing piece" utilize a part-whole conception of fractions. Meanwhile, those students who engage in "residual" reasoning to compare fractions utilize a fraction-as-measure conception. The focus of this article is three-fold: (1) to explain the fraction conception that underpins "gap" and "missing piece" reasoning; (2) to explain why this fraction conception can be problematic; and (3) to provide two instructional recommendations that support teachers in moving students beyond this reasoning and/or limit the potential of it happening.