A centesimal circle and protractor set for upper elementary geometry work, supporting children's transition from concrete geometric exploration to precise angular measurement and geometric construction. The centesimal circle reinforces the 360-degree structure underlying Montessori's sensorially introduced geometry, while the protractor gives children the conventional tool for applying that understanding in layout and verification work. This pairing is well suited for 9–12 classrooms working through the geometry sequence on angles, triangles, and polygon study.