I thought it was refillable, but it turns out it's not. I still don't know the ink's duration, but the marker is as light as a feather. I don't believe the ink will last long.

Good marker. It writes smoothly and doesn't leave any residue - with one swipe of the eraser - even if I erase the board hours after the lesson. There is a claim about the marker that even if someone forgets to put the cap on for a few days, the marker tip doesn't dry out, but I haven't tried it. It is easy to refill from the front.
Useful information:
1. The tip has a writing thickness range from 1.5 mm to 3 mm. To achieve the 3 mm thickness, one must press the tip on the board until the desired result is achieved. Of course, if they later want to write in a smaller thickness, with this specific marker, they won't be able to because the tip doesn't retract.
2. The compatible ink refills are Legamaster (which are more cost-effective) and Edding BT.

Update on evaluation: the initial ink of the marker doesn't last long.