This USB rechargeable eraser from Derwent comes with a built-in 500mAh lithium-ion battery which is recharged by USB for convenience and long-lasting charge. The extra-fine eraser is ideal for fine hairline erasing for detailed artwork and technical drawing. The function button is designed to push on and off when required, allowing for maximum control.Details:GrayRefills are available in packs of 30 erasersErases quickly and preciselyNon-abrasive with circular motor movementEraser is suitable for left and right-hand useSize Information:15 large 5 mm erasers15 extra-fine 2.4 mm diameter erasers