I have an application where we have seen failures on a site glass due to external material (dirt/rocks) impacts. The site glass is ~1" in diameter and made of Borosilicate. Apparently this is essentially "Pyrex". I would like to move towards another material that is more impact resistent, transparent, and able to function with oil splash of up to 120 deg C. I would think something like a Polycarbonate might be an option. Given the dirt environment, would that material lose transparency due to scratches/fading? The purpose of this part is to give the operator a go/no go check of oil in the machine during a walk around. If its not already clear, non-metallics have not been my specialty. Any hints on available materials (and other design considerations) would be great. Thanks.