Over the years she has featured, among other things, rubber flip-flops, a stainless steel lunch kit and wine bottles stopped with natural corks.

这些年来，在其他东西中，她对橡胶人字拖鞋、不锈钢午餐包和天然软木塞塞住的酒瓶做了标记。

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But Curin said researchers, who typically refer in their studies to cheap rubber flip-flops that can be purchased at discount stores, must realize not all flip-flops are created equally.

CNN: Flip-flops present feet with a painful problem

These unmovable surfaces are harsh on bare feet, and the thin rubber sole of many flip-flops does little to adequately absorb the shock they produce.

CNN: Flip-flops present feet with a painful problem

But the rubber soles of most flip-flops just bend all over the place, while the stiff soles of some stylish varieties may not bend at all, she said.

CNN: Flip-flops present feet with a painful problem