These articles may have a natural surface, if obtained from quarry floor slabs of various sizes and thicknesses and machined surfaces, if sawed from blocks. A natural surface. These natural... 
Risers may have natural surface when they are made from flat and thin hollow slabs with machined surfaces, or sawn off blocks (with the exception of flat, semi-gloss surfaces obtained from hollow...
Natural surface clogs are obtained from thin, hollow floor slabs, which are sawn to further reduce their thickness to 1.5/2.5 cm. Clogs with machined surfaces, which are instead derived from blocks...
These articles may have a natural surface, if obtained from quarry floor slabs of various sizes and thicknesses and machined surfaces, if sawed from blocks. A natural surface. These natural...