... 4.0mm Weight: 1ct for 5pcs, 1ct for 7pcs, 1ct for 8pcs, 1ct for 9pcs, 1ct for 12 pcs, 1ct for 17pcs etc. Grade: YWD ... , good diaphaneity, high impact strength and thermal stability, suitable for high grade cutting, drilling, and grinding tools. YWD 2160 ... to middle grade, containing more regular crystal, suitalbe for grinding and free-cutting tools, grinding wheels which work with medium load ...