It is awarded for applying 20 modifications to weapons.
A full list of vendors that supply weapon modifications can be found on the main mod page.
Behind the scenesEdit
|The following is based on Fallout: New Vegas cut content and has not been confirmed by canon sources.|
The cut version of the achievement was named Mod Master and required the Courier to attach all the mods in the game.
|End of information based on Fallout: New Vegas cut content.|