This machine uses round column as its guide slip surface for steady automatic ups and downs Two optional main drive motors (single speed and dual speeds) are upon the clients choice It is applicable to surface grinding and polishing of tombstones, slabs and mosaic which needs to change the thickness frequently The workable for grinding interiorlexterior arcs is available upon customer s request. https://www.wanlongmachines.com/product_cat/stone-machinery/polishing-machine/