Exterminate Casure!! Press as soon as the ink becomes fade! You can also check the ink level as well. Rear knock restores strength. Dry erase marker; Straight liquid type; Line width: 0.08 inches (2.1 mm); Round core/medium design; Color: Blue; Material: Cap/front shaft: PP; Alcohol ink ; Body length: 4.9 inches (125 mm); Shaft diameter: 0.8 inches (21.0 mm); This product is a one-piece, shrink-wrapped.