These 3.00mm x 100mm extra long shank, diamond drills are ideal for drilling 3mm holes in hard materials such as glass, stone, ceramic, porcelain, shell, bone and fossils when the depth of the material requires an extra long shank. These long drill bits prevent your drill from hitting the material whilst drilling. Very popular with lapidarists, glass and stone artists, jewellers, restoration and conservation workers, and Scientists. These long drill bits are solid throughout, not hollow. Overall length: 100mm Diamond Working length: 20mm Diameter: 3mm "I especially find the extra long diamond drill bits helpful because I’m drilling through beach stones about 2 inches thick. I’m using a battery powered Dremel and placing the stones in water. When in water, the bits wear very well" - Andrew Honig