Looking at the Sun with the unaided eye, and nothing else. Every maker states that they are not for use with a telescope, binoculars or a camera, and supplies instructions covering inspection and storage that come with the product.
These are sold in enormous numbers in the weeks before an eclipse, and almost everything worth knowing about them is documentation rather than optics.
What they are
A filter in a cardboard or plastic frame, made for direct observation of the Sun by the unaided eye. Listings cite an international standard covering filters for that purpose.
What the makers say they are not for
Use with any optical instrument. A telescope, a binocular or a camera lens concentrates light before it reaches a filter held at the eye, and these products are not made for that situation. Instruments have their own separate category of full-aperture filters, with their own instructions.
What can usefully be compared
The standard the listing cites; whether the manufacturer is identified on the product; the film construction, which changes the colour of the disc; the frame type, since larger frames designed to sit over spectacles are a distinct product; and the quantity supplied, because these get handed around.
What governs use
The manufacturer’s own instructions, supplied with the glasses. This site reports what makers publish and defers to them.
If this page and the manufacturer’s own documentation disagree, follow the documentation. Every aperture, focal length, payload rating, field, eye relief, transmission figure and thread size on this page comes from the maker’s own published figures, with the unit as printed and the source named. None of it is measured here, and no figure is converted into another convention, because a converted number is a different number. And the limit this page does not cross: no filter, no pair of eclipse glasses and no mounting described here makes an observation safe. The page reports what a maker specifies for its own product — the standard the listing cites, the construction, the fitting, the inspection asked for before use — and what applies to your own equipment is decided by those instructions and by the condition of the filter in your hands.
The questions that keep arriving
How do I judge a listing?
By whether the manufacturer and its address are printed on the glasses themselves rather than only on the packaging, and whether the standard is printed there too. An unattributed pair is an unanswerable question.
Do they have a shelf life?
Makers publish their own guidance on storage, inspection and service life, and it differs between products. That guidance is part of the product and is what to follow.
Last reviewed 17 September 2026