Pierceable cap

A method for penetrating a pierceable cap comprising:

• attaching a shell and an elastomeric seal onto a sample vessel, wherein the shell comprises an access port and a threaded portion, wherein the elastomeric seal comprises a collar configured as an annular ring that is positioned between the access port and the threaded portion wherein the annular ring is held in position and compressed when the shell is attached to the sample vessel, and a support band disposed above or below the collar, wherein the support band has a circumference that is slightly less than an outer circumference of the collar of the elastomeric seal;
• inserting a sample transfer device through the access port in the shell, wherein the shell is attached to the sample vessel by the threaded portion that extends from the access port of the shell, wherein the threaded portion is wider than the access port;
• advancing the transfer device towards an openable portion disposed on a surface of the elastomeric seal;
• puncturing the openable portion with the transfer device to access a sample contained within the sample vessel, wherein the elastomeric seal is configured with a radial portion and at least two ribs extending radially inward and axially downward from the radial portion, wherein downward is toward an interior of the vessel;
• and
• removing the transfer device from the sample vessel.