https://www.tannas.co.uk/staedtler-lumocolor-ohp-pen-non-perm-fine-0-6-assorted-pk4
Staedtler Lumocolor OHP Pen Non-Permanent Fine 0.6mm Line Assorted Colours (Pack 4) - 316WP4
Lumocolor guarantees professional and effective presentation on all overhead transparencies. Not just an OHP pen! - can be used on most other glossy surfaces....