m3 x 5mm socket set grub screws cup point stainless steel 10 pack with 1.5 mm hex key wrench (5mm length) jt custom set screws are commonly used to secure an object within or against another object, such as securing a pulley or gear to a shaft. these set screws are headless screws which are commonly called blind screws or grub screws. these headless screws comes with a hex socket in which a hex allen wrench is inserted for tightening and loosening of the screw. set screws are also used in applications where a flat surface is important, such as handles, grips, surfboard fins, and furniture or machine assembly.