Replacing a lens cap: front diameter and rear mount are different checks

A conventional snap-on front lens cap is selected by the front fitting size; a rear lens cap is selected by the lens mount. Neither is chosen from the camera's megapixels or the focal length printed on the lens. First identify which opening you need to cover.

Three covers that answer different jobs

A front cap does not replace a rear cap. A lens hood is also a different accessory: it is used for shading during photography, whereas the cap closes the opening. Do not choose either from a similar-looking product photograph alone.

Read diameter separately from focal length

Nikon explains that the lens filter size can be found on the lens. Check the maker's specifications when the marking is unclear. In Canon’s accessory chart, filter size, lens-cap code and hood code occupy different columns. That distinction is more reliable than treating every number printed on the barrel as a cap size.

A useful example is the EF-S 55–250mm f/4–5.6 IS STM: Canon lists a 58mm filter size and E-58 II cap. The “55” and “250” describe its focal-length range, not alternative cap diameters. This is a reading example, not a recommendation to purchase a 58mm cap for every zoom.

Make a two-sided cap record

• Front: exact lens model; maker's front-cap code; front diameter; any filter or adapter normally left in place.
• Rear: exact lens mount; maker's rear-cap designation.
• Camera body, if needed: exact camera mount; separate body-cap designation.

Save these as separate entries even if the retailer sells a combined pack. If an accessory changes the exposed front fitting, verify what the cap must actually grip. Do not infer the new fitting from the original lens alone. For unusual built-in hoods or protruding front elements, use the specified cap rather than assuming a standard pinch cap fits.

Compare the right product type

If your documented front fitting is 67mm, compare Buy2Fix's black 67mm centre-pinch camera lens cap. The listing specifies 67mm and describes a centre-pinch design for a 67mm filter-thread fitting. Confirm the exposed fitting and hood access on your setup before ordering. It is a front-cap example, not a rear-mount cap, and no brand authenticity or universal fit is established here.

For contrast, Canon’s RF Lens Dust Cap II is explicitly a rear cap for RF-mount lenses. Its compatibility is stated by mount, demonstrating why a front diameter cannot answer the rear-cap question.

When the size is still uncertain

If the old cap is missing and the lens markings are unclear, identify the complete lens model in its documentation before shopping. Avoid forcing a cap onto a damaged fitting. The useful outcome is a record you can reuse for a spare, not a bag of approximately sized replacements.

Header artwork: photo by Matthew Paul Argall / Wikimedia Commons, CC BY-SA 3.0; full-frame photo in a Buy2Fix layout, shared under the same licence.

Sources and scope

This is a listing-and-documentation buying guide, not a hands-on product test. Product details were checked on 7 November 2026. Confirm the current listing and your equipment documentation before ordering.

• Nikon: identifying a lens filter size
• Canon accessory chart: separate filter size, cap and hood columns
• Canon RF Lens Dust Cap II: rear-cap mount compatibility