The space agency recommends glasses from U.S. manufacturers American Paper Optics, Rainbow Symphony, Thousand Oaks Optical or TSE 17. The glasses must have the "ISO" icon with a designation of ISO 12312-2.
It is also recommended not to use glasses that are older than 3 years, or lenses that have scratches or are wrinkled.
On August 21, all of continental U.S. will experience a partial eclipse for about 2-3 hours. A total eclipse will occur coast to coast within a roughly 70-mile-wide path from Oregon to South Carolina. The total eclipse will block the sun's face for up to 2 minutes and 40 seconds, turning day into night.
Special-purpose solar filters or glasses are necessary when looking directly at a partial eclipse. The only time a solar filter is not required is when a total eclipse occurs. A pinhole projector can also be used to safely view a partial eclipse.