The wire diameter is approximately 3.6mm. The surface is painted. Since the hook part is large, it can be used for a wide range of purposes by hanging it on a bag, belt loop, etc. The opening/closing part can pass up to a thickness of approximately 5.5mm. *Due to the manufacturing process, the interlocking part of the carabiner is not colored because it is difficult to apply paint. *Due to the manufacturing process, there may be small air bubbles in the paint. Please note. *Please note that this is not for mountain climbing.