Made of aluminum and grindstone. The stone is securely attached to a sturdy metal stand, and heavy-duty construction ensures durability. Package includes 12-pack of 3-inch engine cylinder grinding stone replacement stones. Fits 2Inch to 7inch (51-177mm) 3-jaw engine cylinders. These replacement whetstones are designed to clean and polish cylindrical surfaces and service cylinders without cutting or damaging them., Manufacturer: Akfldms