Bell Transitions shield since late 2010 and could not get by without it. Not sure what the true manufacturers warranty is on it but mine seems to simply stop working approximately once a year. I then email Bell Cust Service, explain the situation, given them the MFG Date of the shield and about a week later a new one shows up at my door free of charge. I have been thru 3 now and #4 is on the way. I ride almost daily and I ride a lot of miles. Here in Florida there is so much fine sand on the road that I theorize that the abrasive nature of the sand wears the Photo-chromatic coating off. I use only distilled water to clean it.
Since Bell sends me new ones I am 100% satisfied.
2013 Ducati Multistrada -- Red
2011 Triumph Speed Triple -- Black