Leica push on lens cap question

<p>Hi Guys,</p>

<p>I am a bit puzzled by the sizing of the metal push on Leica lens caps e.g. A36, A39 etc. Can anyone help?</p>

<p>I have an A36 cap and the internal diameter measures 36mm as I expected. I also have what is purported to be an A39 cap but the internal diameter actually measures 42mm. Do the numbers refer to the internal diameter of the caps or something else?</p>

<p>A36 should be 36mm push-on. Sounds like you have an A42 cap. Maybe it's intended as a push-on cap for a lens with an E39 (not A39) filter thread?</p>

<p><em>'Maybe it's intended as a push-on cap for a lens with an E39 (not A39) filter thread?'</em><br>

That's it. You are meant to be puzzled; its a Leica thing. Just be pleased you don't have to drop in 'series' filters any more. </p>

<p>A is for Aufsteck... , as in Aufsteckfilter = slip-on filter<br>

E is for Einschraub... . as in Einschraubfilter = screw-in filter<br>

An A42 lens cap fits over an E39 filter.</p>

<p>Thanks everyone. It appears that I have been given an A42 cap. As David points out, an A42 cap fits over an E39 filter.</p>

<p>Very confusing but at least I know now :-)</p>