These paint pens have been hand built in the UK. They comply with British Standards and COSHH. The xylene based solvent makes the pens usable on virtually any surface, including all metals. In addition, the pigment in the paint reflects the light, meaning they are resistant in all weather. These exact pens are used in the air industry and F1. The pens don’t leak, only take 30 seconds to dry and don’t run when painting.