Gundam Marker Fine Tip Panel Liner (Select - Black, Brown, or Gray) – Gundam Shoppers Network
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)-
GUNDAM MARKER GM01 200 BLACK - Black Fine Tip Bandai Mr Hobby Marker New 4973028935813 | eBay
The Gunpla Panel Lining: Gunpla's Guide to Markers and Paints | One Map by FROM JAPAN