The custom LEGO designs built by 19-year-old David Aguilar aren't meant to sit on a shelf. For years he's been ignoring the instructions that come with LEGO sets to make functioning prosthetic arms for himself, and now he's sharing his creations online, Reuters reports.

Aguilar—who lives in Andorra, a small principality on the French-Spanish border—was born with a rare genetic condition that left him without a right forearm. He built his first artificial limb out of LEGO bricks at age 9, and hasn't looked back. Today Aguilar is pursuing an eduction in bioengineering at the Universitat Internacional de Catalunya in Spain, and he's already on LEGO prosthetic No. 4.

After acquiring complex LEGO sets for things like airplanes and construction vehicles, Aguilar reconfigures them into arms and adds electric motors that allow him to move his fingers and bend his elbow. He documents his building process on YouTube under the name Hand Solo. Each arm he builds is named MK followed by the model number (MK I, MK II, etc.), a nod to the MK suits built by Tony Stark in the Iron Man series.

The LEGO prosthetics are more than conversation starters—they're also affordable compared to professionally made robotic limbs on the market. Aguilar tells Reuters his dream is to one day provide cheaper options to prosthetics-wearers like him.

[h/t Reuters]