“Faron 25” is a project focused on developing a supportive prosthesis for individuals with an undeveloped upper limb for use in cross-country skiing training. The project was inspired by the author’s conversations with Iweta Faron, a former para–cross-country skier, as well as observations of athletes with disabilities. The product is intended for people with congenital upper-limb deficiencies (ranging from incomplete hemimelia to acheiria), as well as for individuals who have undergone amputations of a similar extent. The primary goal of the project is to address the difficulty of maintaining proper posture and symmetrical movement during cross-country skiing. “Faron 25” compensates for the missing limb, improves balance, and extends the glide phase. The product fits within the social and rehabilitative context of adaptive sports, supporting the activation of people with disabilities and contributing to their physical and mental development. The originality of the project lies in the absence of comparable solutions currently available on the market, as well as in the use of a wrist mechanism with a passive range of motion of up to 20 degrees, allowing for a more natural body rhythm. The brace can be easily donned using only one hand.