neck opening 100 formed by lower mold terminus 120 and outer ring perimeter 110 formed by upper mold terminus 130 it should be noted that neck dam 80 in fig3 b is shown for illustrative purposes detached from crown 10 anvil 140 fills the interstitial space of injection mold 60 to give neck dam 80 predetermined thickness by forming cavity 90 chamfer 170 in anvil 140 receives lower perimeter 40 of crown 10 in the embodiment illustrated in fig3 a lower perimeter 40 has alternating rings of apertures 50 a smooth surface 180 and surface variations 55 it should be noted that any combination of alternating surfaces may be used however an enhanced protection factor is achieved by alternating a ring of smooth surface 180 for fluid impermeability with a ring of surface variations 55 or apertures 50 for enhanced mechanical bonding fig4 shows an embodiment of the invention wherein injection mold 60 is formed by two outer molds halves 150 a and 150 b secured by clamps 160 about inner mold surface 140 to form cavity 90 it should be noted that clamps 160 are provided as a simplified embodiment of the invention high volume mold design may employ an alternative embodiment wherein the two halves 150 a and 150 b are aligned and engaged via hydraulic pistons or the like fig5 shows an isometric view of outer mold half 150 a and inner mold surface 140 forming cavity 90 upper mold terminus 130 engages crown 10 lower perimeter 40 and seals cavity 90 so that liquid elastomeric material injected into mold 60 via injection port 70 does not leak out fig6 shows crown 10 engaged with mold 60 it should be noted that alternatively mold 60 may entirely encase crown 10 from top.