Self-tightening key-less feature automatically increasing gripping force, high reliability, and stability. Special quenching treated key parts increases durability. Suitable for drill presses or lathe spindles accept R8 Arbor. Please note, we have pre-installed the arbor to the drill chuck and lubricated together against rusty. Therefor, for first time use, please uninstall the arbor and drill chuck and clean the lubricate to prevent the possible slippery which might cause some run out.