I am in the market for a new visor for my helmet, upon searching ebay I have noticed some of the visors have "tear off posts". I gather they are for some sort of film that you tear off and turf as the shield becomes dirty. I am interested in knowing how these stack up, along with, if the posts inhibit your field of vision in any way. Anyone with experience with tear offs, please let me know your thoughts. And lastly, where are these tear offs sold, I can't seem to find any in ebay, so I'm wondering what they cost on average.