Husna, N. and Nurhasanah, N. 2026. Development of a Didactical Design Based on Research and Development for Teaching Cones and Cylinders to Improve Junior High School Students’ Conceptual Understanding. Interval: Indonesian Journal of Mathematical Education. 4, 1 (May 2026), 26-31. DOI:https://doi.org/10.37251/ijome.v4i1.3211.