For smaller applications the DUO Build System also comes in a 15mm x 15mm square extrusion. The 15mm profile of the 15mm Extrusion has slots on on all four sides that accept standard M3 hardware. Rather than using a T-nut, which is more expensive, slide a M3 hex head screw along the slot and adjust brackets and other build materials as needed.

The flexibility of the 15mm Extrusion makes it a great option for arms, lifts, and other robot manipulators and mechanisms. This is one of the most compact structure pieces and allows for compact designs. Depending on the design and use case, you may wish to add additional supports to avoid twisting under high loads, also known as torsion.