Amazon.com: GSI Creos Black Fine Point Gundam Marker : Toys & Games
G Project - Panel lining! An easy yet effective way to give your models that extra bit of flair. Here are some of the more common options: 1) Panel-lining Gundam Marker (スミいれ用)-
GSI Creos Black Fine Point Gundam Marker GM01– USA Gundam Store
Gundam Marker GM01 Black Fine Line - Entertainment Earth