This lens cap is for optical instrument such as telescopes, spotting scopes or giant binoculars.
Internal Diameter: 102mm (Note: the size is measured as internal diameter of the cap, which is equivalent to the external diameter of the lens including the lens housing).
Depth: 14mm
Material: Rubber.
Note: This listing is for ONE lens cap as described above (not for a pair). This lens cap is made of rubber material which is flexible. This feature enables the cap to cover lenses with external diameter bigger than 102mm (can add 1-2mm in diameter).

Note: The size of the lens cap is measured as Internal Diameter of the cap, which is equivalent to the external diameter of the lens including lens housing (as shown in the picture above). Please allow a small difference in measurement (eg. 0.5-1mm). A rubber cap can normally fit a slightly bigger lens than the specified size (eg. +1mm to 2mm depending on actual size).
If a cap is slightly bigger than the external diameter of the lens housing and there is no matched cap size available for the lens, you may consider putting an adhesive cloth tape around the internal edge/rim of the cap. This can often secure the cap on the lens.