The adapter features an external square drive enabling it to hold sockets with an internal square drive, which would normally only fit impact driver. This product is intended for heavy-duty screw-driving applications such as plant installations or heavy industrial work. All adapter extension bars are outfitted with a spring-loaded ball detent that locks onto sockets to ensure a secure fit into the driver head to prevent slipping or loosening when applying torque to regular nuts, lug nuts and bolts.150mmMade of high strength impact grade chrome vanadium steel and coated with corrosion resistant black manganese phosphate, this impact socket adapter set will last for years in your toolbox at home or the garage.