... Weight: 1ct for 5pcs, 1ct for 7pcs, 1ct for 8pcs, 1ct for 9pcs, 1ct for 12 pcs, 1ct for 17pcs etc ... 70 for different purity. YWD 50 and 70 is the best quality stones made in lab condition ... , high impact strength and thermal stability, suitable for high grade cutting, drilling, and grinding tools. ... diaphaneity and low impurity, high strength, suitable for circular saws, frame-saw and geological broaches. ...