Made of a proprietary Mylar film, the filter is ISO 12312-2 compliant for safe solar viewing, blocking 99.999% of intense light across the entire visible spectrum and 100% of harmful ultraviolet (UV) and infrared (IR) radiation; resulting in high-contrast views of the sun in a neutral color. At just 4.2 ounces, the filter will provide the safety required to observe the sun and all phases of a solar eclipse without adding significant weight to the front of your OTA.