This is the Gundam Real Touch Gray #3 Paint Marker by Mr. Hobby.
This marker can easily express dirt and blurred paint with a realistic touch. A water-based wipe-off type is used for safety. Equipped with two types of nibs, fine and thick. GM400 is a pen for blurring already painted GM401-410. Use it to blur the boundary surface. If the nib gets dirty, clean it with a tissue. If it becomes difficult to remove the dirt, use a new blurring pen.
Gundam Marker: GM406 Real Touch Marker Gray 3 (Renewal)
GUNZE – Page 15 – Trainz
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