Fotodiox Metal Rear Lens Cap for M39 L39 Screw Mount Lenses Leica LTM Black

Old screw mount lenses often turn up without a rear cap: it is missing from a second-hand buy, or the brittle plastic original no longer grips. That leaves the rear element exposed in your bag, and dust finds its way in through the thread. The Fotodiox metal rear cap screws onto the 39 mm thread and closes off the back of the lens properly.

• Rear cap for lenses with M39/L39 screw mount (Leica Thread Mount, LTM)
• Hard anodized aluminium, black
• Protects the rear element and thread from dust, scratches and pressure
• Slim and light: 4.2 cm across, 1.0 cm tall, approx. 9 g

A clean rear element and a clean thread

Metal instead of brittle plastic

The cap is made of hard anodized aluminium. It will not get crushed in a full camera bag, it does not rust, and because it screws on rather than pushing on, it stays put even when the lens is rattling around with the rest of your kit.

Less dust inside the lens

An open thread is a direct route into the lens. With the cap screwed on, the back stays sealed, the rear element stays free of fingerprints and the fine thread is protected from knocks.

How this works in practice

Rangefinder classics on a mirrorless body

You are adapting an old screw mount lens to your mirrorless camera and swapping between two or three focal lengths on the go. Whichever lens is off the camera gets the rear cap screwed on and goes into your jacket pocket. At around 9 g, you will not notice the cap is there.

The collection on the shelf

Lenses in storage collect most of their dust at the open rear. A matching metal cap on every screw mount lens keeps the collection clean and looks tidier than a mix of old caps.

What you should know before you order

Screw mount only, not bayonet

The cap fits the M39/L39 screw mount. It is not suitable for Leica M bayonet or M42 lenses. It is not a front cap either: a 39 mm filter thread on the front of a lens has a different pitch.

Slim profile

The cap is only 1.0 cm tall on the outside. For lenses whose rear element sticks out well beyond the thread (some wide-angles and collapsible designs), measure the protrusion first.

A single rear cap

You get one rear cap. No front cap or body cap is included.

Technical details at a glance

• Type: screw-on rear lens cap
• Mount: M39/L39 screw mount (Leica Thread Mount, LTM)
• Material: hard anodized aluminium
• Colour: black
• Dimensions: 4.2 x 4.2 x 1.0 cm
• Weight: approx. 9 g
• Manufacturer part number: RC-M39-BLK

Scope of delivery

• 1 x Fotodiox rear lens cap M39/L39, black