Nån som vet vad detta är?

[Delfintua]

A closure having a stopping mechanism whereby a stop lug is positionable between a flexed and unflexed position relative to a spring
gap. The stop lug may project from a skirt of the closure top wall. The spring gap is positioned adjacent the stop lug to provide an area
for the stop lug to travel when outside forces are applied to the stop lug and subsequently return back to the unflexed position. The
stop lug may have a substantially vertical support rib in combination with a plurality of annularly spaced ribs.