1.    Enamel and Cast Iron 
1.    Thickness of enamel: 0.8-1.5mm .Thickness of cast iron: 7-9mm
2.    Enamel-coated cast iron is the most durable material for bathtubs.
3.    The thickness of the cast iron and vitreous enamel surface makes its surface resistant 
4.    to acids and alkali, providing outstanding protection against chipping scratches and dents.