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Non-impact protectors are those which do not pass all high-impact testing requirements and are therefore marked only with "Z87" (no "+" sign). The U.S. military standard requires (at a minimum) that ballistic eyewear can always withstand a 0.15 caliber, 5.8 grain, T37 shaped projectile at a velocity of 640 to 660 feet per second (approximately ...
Safety glasses can often mount insert frames to mount prescription corrective lenses for users with suboptimal vision. Such insert frames are mounted behind the protective lens. In some applications, regular eye wear, if manufactured from high-impact materials, can be worn with removable side shields.
Polycarbonate is commonly used in eye protection, as well as in other projectile-resistant viewing and lighting applications that would normally indicate the use of glass, but require much higher impact-resistance. Polycarbonate lenses also protect the eye from UV light.
CR-39 is the most common plastic lens, due to low weight, high scratch resistance, and low transparency for ultraviolet and infrared radiation. SR-91 is a proprietary material that was introduced by Kaenon Polarized in 2001. Kaenon's lens formulation was the first non-polycarbonate material to pass the high-mass impact ANSI Z.87.1 testing.
Guitar slide made of borosilicate glass. Borosilicate glass is a type of glass with silica and boron trioxide as the main glass-forming constituents. Borosilicate glasses are known for having very low coefficients of thermal expansion (≈3 × 10 −6 K −1 at 20 °C), making them more resistant to thermal shock than any other common glass.
Rimways fare much better with CR-39 because the arches absorb shock and stress. The implementation of polycarbonate—the material used to make bullet proof glass—in addition to making rimless glasses even lighter, reduces the glasses' fragility as polycarbonate can endure a great amount of stress and is highly impact resistant.
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CR-39 is about half the weight of glass with an index of refraction only slightly lower than that of crown glass, and its high Abbe number yields low chromatic aberration, altogether making it an advantageous material for eyeglasses and sunglasses. A wide range of colors can be achieved by dyeing of the surface or the bulk of the material.