.For the skilled mechanic or engineer. Can be used with 17mm & 19mm spanners with the hex drives on the top of the socket. The extractors are the concentric roller bearing type that won't damage the thread on the stud. They can used for stud removal and stud fitting with no damage to the thread. Very professional. Diagrams and step by step instructions included. Look at the attached pictures to see the actual quality of these. Made by professionals for professionals. Specifications • Sizes: M6 x 1.0, M8 x 1.25, M10 x 1.25 and M10 x 1.5 • High quality Chrome Molybdenum Steel • black phosphate finish • Blow moulded case • Stud extractors individually labelled with size • Professional finish