3D printed parts needed to build an airtight dry box for 3D printer filament storage. Full instructions can be found at this link to my How-To at Instructables.com.
The purpose of this dry box is to prevent printer filament from absorbing moisture in the air. It can be used for keeping filament spools of various sizes (up to ~10" [260mm] diameter) in long term storage and in active use. It also prevents dust and dirt from entering the print head by a foam filter. Lubrication can be added as well, as some people in the 3D printing community have suggested. The PTFE tubing is a nice benefit of this set up, even without a bowden style filament drive, as it prevents kinks and coils from stopping the print.
Print settings are just my preference. Other settings may work just as well.