Frangible cap for bottles

A frangible sealing cap for a bottle neck, comprising:

• a. a plastic cup having a top cover and a depending annular skirt, the cover and skirt having thin walls, the skirt being free of annularly outward bulge structure, said skirt and cover each having wall thickness between about 0.010 and 0.030 inches,
• b. a plastic pull tab integral with the skirt and depending to a level below the lowermost level of the skirt, and
• C. there being two weakening score lines extending into, but incompletely through the skirt from the outer surface thereof, said lines extending upwardly toward the top cover from points proximate the junctures of the skirt with opposite edges of the tab,
• d. the skirt being thickened at circularly spaced locations to define narrow reinforcing protrusions which are elongated in directions toward the top cover and which stand outwardly from the outerside of the skirt, the protrusions confined to the lower half of the skirt, said score lines located adjacent two of said protrusions but at the inner sides thereof closest the main extent of the tab, whereby the skirt material between the score lines is uninterrupted by any of said protrusions.