Set contains4 fine nib sizes: 0.03, mm 0.05 mm, 0.1 mm, and 0.3 mm. These fine-line pens are compatible with Copic Marker Ink. They are not affected by alcohol, so you can use Copic markers or other alcohol marker over the top of them. They are waterproof, archival and photocopy safe. They are NOT refillable.