Poor build quality, I am rather disappointed in this product.  I've owned Mizuno products prior and they were all of superior quality but this shoe is any but.  I've owned the Wave Rider 15 previously and they were an amazing shoe, especially for sprinters.  This show is ideal for neutral runners, but it is NOT anywhere as durable or as 'stiff' as most sprinters would like.  After just 3 months the show began tearing at the mess lining, keep in mind I'm on the track only 4 times a week doing no more than 1600m combined work.  Would not be looking to Mizuno for future sprint trainers.