Is the Pilot 45100 marker refillable?

Yes, the Pilot 45100 Super Color Jumbo Marker is refillable.

What type of ink does the Pilot 45100 Super Color Jumbo Refillable Marker use?

The marker uses a fast-drying, waterproof, low-odor ink that is xylene-free.

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Pilot 45100 Super Color Jumbo Refillable Marker, Extra Broad Marker Point Type - Chisel Marker Point Style - Refillable - Black - 1Each