Ok so I bought a new Viper RS-V131 Bluetooth helmet and decided that as with all helmets that an anti-fog insert would be required. First off I have used Fog City inserts in the past and i have to say that the Oxford version is a lot flimsier and of course it doesn't have the reactive tinting, but it is a lot cheaper. Fitting was pretty easy but it does buckle easily when you are trying ot get a decent fit, there are protective covers front and rear that peel off easily. If works, after a fashion. I ride every day, wind rain and freezing temperatures are very common (Winter, Cumbria) and it does do the job to a degree. But it seems to mist up when stationary in traffic and can be a little tricky to clear. Overall not bad, but if you get rain inside then when you try to wipe it the visor buckles and can easily be creased. Mine seems to have stuck OK(ish) you can pull it off and reposition if you need, but unless they come with superglue than i think they are all pretty much the same. Due to the thinness of the material it seems that the edges are prone to a slight whistle if you have any sirflow under the visor at speed.
For cost its not a bad item, but I think next time i might shell out a little extra for a better quality item.