How to take apart Ozito airbrush??

[Jasonho]

Hi all. I purchased the Ozito airbrush and mini compressor kit (Mack 300) and I can't undo the air cap body and the valve body parts (see pic). The spanner supplied is a square shape (see other pic) while the parts are round?? Any suggestions?? And why is there a square spanner when all parts are round? 🤷