These Derwent electric eraser refills contain 30 refills in total, including 15 large erasers that are 5mm in diameter and 15 extra fine erasers that are 2.4mm in diameter. The large erasers are good for general erasing especially when finesse and accuracy aren\'t particularly important. The extra fine erasers are ideal for fine hair line erasing and are suitable for detailed artworks especially technical drawings. These refills fit the Derwent Electric Eraser USB Rechargeable Kit. - Brand: Derwent - 30 pack (15 large 5mm diameter & 15 extra fine 2.4mm diameter) - Refills for the Derwent Electric Eraser USB Rechargeable Kit - Extra fine erasers are perfect for detailed and accurate work - Large erasers are ideal for generic everyday use