It appears that when these caps were reproduced a few years ago, the maker must have felt, and rightly so, that the rear main cap was too complicated to reproduce. I have seen a few of these sold but I have no idea about their integrity for metallurgy If the intention is to pass them off as original, that will not work. The Mexican caps will fill the bill for your extra strength you are seeking and at least that way you will have all five caps, although obviously different from original Hipo caps. If you decide that you need the real deal Hipo main caps, I do have a few sets.