The goal of this single-subject research design (clinical trial) is to assess the functionality of the 3D printed prostheses and to compare them to the existing prostheses in terms of mobility, balance, utility, and comfort. Participants who have a unilateral or bilateral transtibial amputation wear their existing prosthesis for roughly 3 weeks, followed by 3 weeks wearing a 3D printed prosthesis. The research assistants collect data throughout each period remotely, with the exception of one in-person visit to participants' homes to prepare the setting for the virtual evaluation sessions.