Finally, a quality wheel with enough versatility to handle your job needs. Available in Soft and Hard Bond. You finally have the tool that can be matched for very hard concrete or a separate wheel for sandstone, asphalt or green concrete and very abrasive masonry, grouts, etc.SOFT BOND- for very hard concrete grindingHARD BOND- for soft and abrasive sandstone, asphalt, green concrete, abrasive masonry and groutsAvailable in either 7/8-5/8" Open Arbor or 5/8-11" Threaded Arbor