I find that this can produce some amazing results, but I am not sure if it is plastic dependent or what.  The instrument cluster lens in my 72 Vega was really cloudy.  This was the first time I tried this and the results were amazing.  The lens looked like new!  I tried it on headlight lens, and although it made it better, it wasn't as dramatic as the previous use.  I have used it on several items, and it always works, but sometimes it works amazing, and sometimes it is so-so.  Overall, it is a very good product.