PIRO is a lightweight, thin-shelled ankle-foot orthosis designed for children affected by cerebral palsy. It is designed within seconds and manufactured by 3D printing for a perfect fit. The shell with variable thickness provides strength yet flexibility and comfort. Designed as a breathable structure, the perforated thin wall reduces the weight by up to 70 per cent. Due to its slim proportions and low-profile strap fastening, children can easily wear the orthosis with their favourite pair of shoes.