A mold for forming a prosthesis is disclosed. The mold can include a stem portion, a head portion, and a securement assembly. The stem portion and the head portion can be provided in a kit having a variety of different interior dimensions so that a user can select or customize a mold cavity size based on the dimensions of a particular implant site of a patient. While a set of stem portions and head portions can have interior dimensions of varying sizes, each of the stem portions and each of the head portions can have the same or similar exterior dimensions for attachment using a common securement structure. Related methods are also disclosed.
