SUMMARY
This study aims to produce products in the form of learning media and instruments based on the 5E learning cycle model on harmonic vibration material. It is development research using the ADDIE model consisted of 5 stages: analysis, design, development, implementation, and evaluation stages (this study was limited to the development stage). The products developed were Syllabus, Lesson Plan, Student Worksheets, and Critical Thinking Skill Instruments in Physics. The feasibility of the learning media and instrument developed was measured by three experts’ validation by calculating the validity and reliability values of the media and instrument. The validity results based on the experts’ assessment showed that the score of the syllabus was 3.70 with very valid criteria. The Lesson Plan was 3.66 with very valid criteria; the LKPD was 3.66 with very valid criteria, and the Critical Thinking Skill Instrument in Physics was 3.63 included in the very valid criteria. The reliability results of the syllabus were 94.52%, the Lesson Plan was 90.36%, the LKPD was 91.78%, and the Critical Thinking Skill Instrument in Physics was 93.62%, indicating that all aspects assessed had a reliable category. Based on these results, it can be concluded that the learning media and instrument developed are feasible to use in learning to improve students' critical thinking skills in Physics on harmonic vibrations material.