A self-adjusting holster includes first and second shell portions having opposite side panels extending substantially parallel to each other. At least one of the first and second shell portions having a bottom panel. The side panels of the first shell portion and side panels of the second shell portion are configured to telescopically mate such that the mated shell portions slidably adjust relative to each other in a first direction and together define an interior space and an open end opposite the bottom panel. An elastomeric member is configured to bias the shell portions toward each other along the first direction. An item inserted into the open end between the first and second shell portions displaces the shell portions relative to each other against biasing force provided by the elastomeric member.