What you will get are digital files, including STEP and DXF formats. This sliding iris diaphragm is similar to a shutter mechanism. The shape is like Chinese ancient copper coins-a circle with a square hole. There are four blades.When you move the Driving Button,the blades in the center square hole can open or close gradually. Most parts are designed for laser cut. You need to prepare some metal parts,such as bolt, nut, pins,refer to the BOM in the package. The square hole is 40x40 mm, the outer diameter is 175 mm, and the mechanism's thickness is 12 mm. Ignore FBX, STL and obj format files, they are only used to meed cgtrader's requirement.Parts' thickness is 3 mm. Tutorial of assembly steps: https://www.tanerxun.com/assemble-square-hole-type-sliding-iris-diaphragm/.html