For FDM production, supply STL, STEP, 3MF or OBJ together with the intended dimensions in millimetres. A file extension alone does not establish manufacturability: the workshop checks the geometry, machine fit and intended use before quoting.
For laser cutting, supply vector paths in SVG, DXF, PDF or Adobe Illustrator format, with the material thickness and required quantity. For engraving, provide vector artwork or specify plain text, names or serial numbers.
Reference images can explain a task but do not define the complete geometry. For one simple part without CAD, choose the prototype service from AED 800: one model, one correction before manufacture and one physical sample.