Difference Between with Skin and Without Skin

you can compare the difference between with Skn and without Skin from the picture picture number 1 / without skin made by cutting process from sheet. cutting shape and size as customer's request. as you see, there is no skin on round surface picture number 2 / with skin made by specific mould ( 75 dia ) in 1200mm length, then cutting in 10mm length. as you see, there is skin on round surface