A bone marrow aspiration apparatus comprising a hollow stylet removably positioned within said needle a cylindrical threaded section a depth gauge threadedly engagable with and movable longitudinally along the threaded section and having a proximal and distal ends, the proximal end being spaced a variable first distance from the end of the needle a locking nut movable along the threaded section a cap connection section having a fluid fitting therein a cap engagable with the cap connection and engaged with the stylet wherein the threaded section and the depth gauge define a stylet passage between the fluid fitting and the proximal end of the depth gauge and wherein the variable first distance between the end of the hollow needle and the proximal end of the depth gauge corresponds to a position of the distal annular end of the depth gauge relative to the threaded section.
