Cán cầm mũi vít (screwdriver bit handle) lục giác

If the bit does not fit smoothly try to pre-heat the tip of the handle with a heatgun or an hair dryer, before inserting the bit**.** Then leave the part to cool down with the bit inserted. That will make the perfect  size to match. Better use a brim.

On the examples shown I printed on PETG, 100% infill, 4 perimeters, sanded and applied  bicycle chain oil on them.