After giving up on trying to keep the lexan shield on my 1665 clean, I gave up and made a new one of expanded steel. I've got about 12 hours on it an so far like it better. The biggest issue I had with the lexan sheilds was keeping them clean and scratch free. In sunlight, there was simply too much glare to see what I was doing. I found myself leaning over and looking around it all of the time. Small particals and dust can still pass through but I still felt it was safer than looking around the shield all of the time. I do wear a face shield,(trying to remember to flip it down all of the time).