5815556160749568 Felix Puzzle 智趣坊 Cast Helix 華 The grooves engraved in the two rotating boards are called "logarithmic spirals." These two grooves always cross at right angles, and a square hole is formed at Product #: felixpuzzle-Cast Helix 華 2022-09-26 Regular price: $HKD$100.0 Available from: Felix Puzzle 智趣坊In stock