Original small clear glass lenses with a large flat trim ring. I believe these might be from heavy binoculars or an actual sight of some kind. Like the other lenses, I have given up on attempting to figure out exactly what they go to. These are new old stock from a warehouse with wear and dirt from age and storage. Price is for 1 lens.
Please only measure by the metric readout on the calipers, the standard side of this set is of a bit.