Very thin rubber on the sole-side, has worn off after 4 months of medium use (~4000 steps/day; half of that indoors, on carpet).<br />By &#34;worn off&#34;, I mean there is a hole through the sole in the big toe region, on both shoes (not from a puncture).<br /><br />This has never before happened to any shoes or sandals I've owned, so I attribute this to poor material quality.