Ive seen it everywhere this shoe is reviewed. It collects and keeps small rocks with every single foot step. The rocks are tiny and I personally do nothing to remove them. The insole is a little dodgy when it comes to staying put when you slip the shoes on. Other than that it looks and performs just great for me as an older beginner runner. The Flyknit and flywire tech are an upgrade and definitely worth What they do for comfort and performance.