The filter has a neutral density of 5, which blocks 99.999% of all light, including harmful IR and UV rays.
Proper use and care of sunscreen will ensure a very long life. Through the filter, the sun appears in a natural yellow-orange color. Depending on the size of the optical instrument, you will see solar granulation (solar photosphere) and sunspots. Mercury transits and solar eclipses can be safely observed through the filter.
The actual filter consists of a 0.05mm thick Helios Solar Film® sheet.