Under4L packs a Mini-ITX layout into a two-part printed enclosure

A small footprint comes with a tightly defined parts list in Marcos Ponce’s Under4L, a 3.73-litre Mini-ITX enclosure also called Stak 3.7. In his firsthand design log dated August 30, 2026, Ponce documents a project built around two printed sections secured with four M3 × 6 mm screws.

Space saved through stacking

The layout stacks a low-profile graphics card and Flex ATX power supply on the same side of the motherboard. Ponce lists a 37 mm CPU-cooler limit and graphics-card dimensions up to 182 × 69 × 36–40 mm. A graphics-card build requires a 200 mm PCIe riser; he reports testing a Gigabyte RTX 5060 Low Profile.

Those limits make component selection central to the project’s appeal: the compact enclosure leaves little room for substitutions.

Six revisions to simplify the shell

According to Ponce, the design evolved from 4.7 litres and seven printed components through six revisions. Its structural section uses ABS, while a separate outer shell allows customization. His reported printing times on a Bambu P1S range from approximately 12 hours to around 22 hours, depending on finish and wall settings.