It is a digital product, what you get are STEP and DXF format files. You can fabricate parts and assemble the mechanism by yourself. It is similar to a shutter mechanism. When you move the Driving Button,the four blades in the center square hole open or close gradually. But it is a sliding type. The shape is similar to Chinese ancient copper coins-outer is a circle and center hole is square. Most parts can be fabricated with a laser cutter or cnc router. Some metal parts need to prepare,such as bolt, nut, pins,refer to the BOM in the package. The square hole is 100x100 mm, the outer diameter is 310 mm, and the mechanism's thickness is 12 mm. Part's thickness is 3 mm. Ignore STL, OBJ and FBX format files, they are only for cgtrader's requirement.Free 3DPDF file are downloadable：https://twothreed.comIf you have trouble to assemble the mechanism,read this article: https://www.tanerxun.com/assemble-square-hole-type-sliding-iris-diaphragm/.html