Iris mechanism or taiji mechanism designed for 3d print. There are 2 leaves. Then you rotate the Drive Partor the middle plate, the center hole can open or close gradually. The center hole is diameter 60mm, the outer size is diameter 140mm and thickness is 12.5mm. To assemble the parts togther,some M2 screws are needed.Parts are designed for 3d printing. It is best to use resin material when 3d printing. And you may need to sand some parts due to the 3d printing quality.Parts should be printed separately and then assembled together.The FBX and OBJ format files can be deleted,they are only for cgtrader's requirement.