I'd LOVE to get my hands on one of these beautiful OV-15s. I see this one has an acrylic lens too instead of glass.

I like glass lenses 'cause plastic lenses tend to eventually turn brown after a long life of usage.

Isn't it mainly Polycarbonate lenses that Suffer yellowing?? I Believe Arcylic doesn't really Yellow at all...my observation it only seems to become slightly hazed with Age. i Prefer glass indefinetly.

Devonte is correct, only polycarbonate yellows. Acrylic will never yellow. Sometimes they haze but under normal conditions it won't necessarily. When brand new, polycarbonate has a more glass-like appearance since it's shinier whereas acrylic is duller. But the shine fades once the lens begins to yellow.

I prefer glass for MV (more so for vintage fixtures) and will only use glass with MH but for HPS I like both, leaning more toward plastic since that's what's used here. I'm not a fan of polycarbonate though. I like acrylic plastic lenses.

I've seen acrylic refractors yellow before. Especially when they are used improperly, like higher wattage luminaires I've actually seen them melt.

If the lens gets hot enough the point of melting I'm sure it will discolor a little but when used properly, they will never discolor. Polycarbonate on the other hand discolors in normal use. There are plenty of 100W MV fixtures here (yes, just 100W!) with practically brown refractors after years of UV exposure. And we have always used phosphored lamps! The key advantages of polycarbonate over acrylic (and the only advantages really) are that it is more resistant to impact and can withstand higher temperatures, however once the refractor discolors, its vandal resistance becomes less than acrylic.