This rust eraser removes rust from cast iron and steel. It is a semi-flexible rubber sanding block with 120 grit impregnated uniformly in the block. We find it very useful for removing superficial rust from our scythe blades on the odd occasion we forget to give them a light oiling after use . The block is a comfortable size to hold in your hand, being 80 mm x 50 mm x 20 mm. Unlike other sanding blocks, it retains its abrasive qualities until the block has been completely worn away – just like a pencil eraser.