Background: This study investigates the models of elementary content specialization (ECS) in elementary mathematics and science and the affordances and constraints related to ECS--both generally and in relation to specific models. Elementary content specialists are defined as full-time classroom teachers who are responsible for content instruction for two or more classes of students. The sample consists of 34 elementary content specialists in math and/or science, as well as a matched comparison group of self-contained classroom teachers. Participants participated in a focus-group interview and an online survey. Qualitative and quantitative analyses were performed to determine the models of ECS present in the sample and the affordances and constraints related to ECS as compared to traditional, self-contained classrooms. Results: This research differentiates six models of specialization, characterized as "within-grade team teaching," "across-grade team teaching," and "science as a special." Comparisons of data from math and science teachers engaged in ECS with self-contained teachers indicate that content specialization has affordances related to planning time, professional development, and instructional time. Constraints related to ECS include limitations on flexibility and the ability to collaborate with other teachers around content. No significant differences are found for time spent in transitions and most comparisons related to meeting the academic, social, and emotional needs of elementary students. Conclusions: Engagement in ECS generally, and different models of ECS specifically, present various affordances and constraints. Differences between self-contained and ECS structures are magnified by certain models of specialization, such that these models can be placed along continua for these factors. There seems to be a trade-off with these factors in ECS implementation, such that easing the role of the teacher in one area amplifies it in another. A variety of factors may contribute to teachers' and administrators' decisions to engage in ECS. These continua of factors may support teachers and administrators in their decision-making as they consider alternative instructional arrangements to the traditional, self-contained model.