There is rust. I've never done pottery, so this is a novice's assessment, but the rotation seems smooth. Diameter is 22 cm. Measurements are approximate, so there may be some error. Please understand that there is rust and dirt before purchasing. If you have any questions, please feel free to ask. I will upload photos. This is a used item. There are scratches and dirt. Please refrain from purchasing if you are sensitive to these issues. Please check the condition in the photos. Shipping will be done with simple packaging. Recycled packing materials may be used.