32 mil. 60 Grit Silicone Carbide. High traction, anti-slip, watersproof, coated with an aggresive pressure-sensitive acrylic adhesive. For use indoors or outdoors; on walkways, ramps, stairways; in machine shops, work areas, etc.; to comply with OSHA 1910.263(3) 3" core.
A "mil" is a unit of thickness equal to one thousandth of an inch.
To convert mil to inches take mil & divide by 1000.