I bought these glasses because I have tried other X Loop glasses before (the ones with the vents at the top of the lens).  I liked these glasses because they don't have a rim across the top which is PERFECT for riding in an aero position on my road/tri bike.  I love them, but after only a week they were falling apart.  I bought a repair kit from a kiosk at the mall (cost more than the glasses - $5.99) and I was able to fix them and tighten all of the screws/bolts.  I have had the glasses for about a month and I'm happy with them, but I would suggest making sure you can tighten all screws/bolts so that they don't fall apart.