Equipped with a hollow out mono eraser. ● Please select the model number ER-MG (P.525). Ball diameter: 0.02 inches (0.5 mm); Sharp lead diameter: 0.02 inches (0.5 mm); Length: 5.9 inches (150 mm); Shaft diameter: 0.7 inches (18.5 mm); Ink type: Oil based dye; Refill: BR-CAE; Replacement eraser: ER-MG