Use 30 rectangle (A ratio) sheets of A4 paper.
Difficulty : ⭐⭐⭐
Time: 2 hours
Ruby Unit designed by Nick Robinson.
Model paper size:
Unit (brown) : 5.25 cm x 7.4 cm (divide A4 to 8 pieces)
Model height: ~ 12 cm
PrwOrigami - Kusudama Collection
Ruby Unit Kusudama
Search for "Ruby Unit Nick Robinson Diagram" in Google.