Q: How about quality assurance & after-sales service? A: We are committed to providing customers with high-quality products and excellent services. If you have any questions about product specifications and usage methods, you can contact us; if you have not received the package, the products damaged due to the logistics, or you are not satisfied with the product itself, please contact us, we will give you satisfied reply and solution within 24 hours. Looking forward to your purchase and experience of our product Specification: Material: Diamond Name:Wet Diamond Core Drill Bit Type:51*370, 56*370, (63*370, (71*370)(Optional) Package list: 1 x Wet Diamond Core Drill Bit Note: Water drill: water must be added in the process of use, and it should be used for core-cutting project. It is suggested to be matched with fixed or hand-held drill Drill bit installation: firstly, check whether the spindle is swinging and whether the electrical and mechanical parts are normal. Drill bit is loaded to ensure that the drill bit is clamped with the drill and remains concentric