Abstract: A device includes an outer body and an inner region defined by the outer body. The inner region may have a first end having an opening therein and a second end. The inner region may comprise a first portion and a second portion, the first portion positioned adjacent to the first end, the second portion positioned adjacent to the first portion and the second end. The first portion may be shaped to define a pin receiving portion for receiving the tip of a pin. The first portion may be comprised of a first material having a first density, while the second portion may be comprised of a second material having a second density. The first portion may contain a non-linear inner surface bounding the pin receiving portion. The inner surface may contain one or more protrusions extending therefrom, on one or both sides.