It is an iris mechanism- three blades(mechanical iris). There are STEP and STL format files in the attachment. These 3d models can be 3d printed.The size is D65X10 millimeter, and the center hole is D25 millimeter.Ignore the OBJ and FBX format files, they are just used to meet cgtrader's requirement.If you need more mechanical models, please visit:https://www.cgtrader.com/monk3947And if you need help, maybe we can give a hand:https://www.tanerxun.com/services