The present study aimed to examine the opinions of in-and preservice middle school mathematics teachers about teaching four operations with integers through "number line" and/or "counters". Participants were 42 middle school mathematics teachers and 51 pre-service mathematics teachers. The data were collected through open-ended interview questions. In data analysis, a content analysis technique was used. The results suggested that the number line was easier and more understandable and that the 'zero pair' contributed to conceptual understanding. It was also found that the use of these models in different operations with integers was due to different reasons. The recommendation of using traditional methods (eg memorization of rules) took its place in the study as another interesting result.