Thin Wall Multi-Layered Electroplated Diamond Core Drills, Manufactured by UKAM Industrial are Multi Layered. They have 3 layers of diamonds, not just 1 layer of diamonds like conventional electroplated drills. This provides longer drilling life, smoother surface finish, faster and freer drilling action, & more consistent performance. Recommended for drilling full range of glass, quartz, optical materials, composites, soft to medium hard natural and semi-precious stone, as well as softer Advanced Materials. It is highly recommended that these diamond drills be used with water swivel adapter Model 5811, 5811S or 58MF to run high pressure of coolant through center of drill.