Exell MRB400 1.35V Zinc Air Battery Z400PX, E400N, EPX400, H-B, KX400, MRB400, PM400R, PX400, RM400, T400N, V400PX

This battery works perfectly in my Pentax Spotmatic SPII. If you put it in and the meter works in reverse, flip the battery around. That's a fun little quirk of the Spotmatic meter that I'm glad I read about in advance, because I would have been so confused when it happened to me!

Bought this for an old Pentax Spotmatic and it works. I haven’t used it long enough to know how long it’ll last. It’s not like I’m using the camera constantly so I imagine it’ll last long enough for my purposes. No complaints.

Worked great in my camera! Very happy.

I got this battery for the same reason almost everyone else here did, for the light meter in an old Pentax camera. Unfortunately the battery was completely discharged when I got it. I made sure to read the details on the back of the packaging, removed the little sticker blocking the air holes, and let the battery sit for hours and the voltage never went up higher than 0.2V. I kept checking it with a multimeter and confirmed that the battery was dead.Instead of taking a chance on these batteries for your old camera, I would recommend using a light meter app for your phone and using your camera without its light meter.

I used this battery in my 35mm Honeywell Pentax Spotmatic camera light meter. It works well. Traded the camera in.

Finally, I found a battery that works with my father's old Pentax Asahi SP1000 light meter! It is a small battery (diameter) with a plastic collar, which is a little bit fragile. But it works! Light meter back to life and accurate!

Used Wein cell 1.35v MRB400 mercury replacement battery to replace now-banned RM400R or V400PX mercury batteries on my 1970 Asahi Pentax Spotmatic II camera. I experienced two problems: (1) The battery is delivered with a black plastic sheath around its edge. This gives the battery the *appearance* of the original shape, but makes it too tall to fit into the Pentax's battery compartment. (2) With the plastic sheath attached, the polarity of the battery was reversed from what the camera expected to find (i.e., the part of the battery meant to point to the inside of the battery compartment (which is narrower) is supposed to be positive.I could not find any information in the Weinproducts.com, so after confirming battery voltage and polarity with a voltmeter I tore off the plastic sheath surrounding the battery. This revealed a significantly smaller battery which although rattled inside the camera compartment like a quarter in a lunchbox, did make the camera light meter work (presumably accurately -- I have not tested it).I could have saved a lot of effort if Wein had put a comment in this battery's page that the dimensions of their battery may not match the original and that the sheath (which could be removed) may give the battery a shape similar to the original but may give it a slightly different dimension. This is not a technical problem, but it is a technical issue because peculiarities of the product which could end up costing the client time were not pointed out. For this I am rating the product three stars.

Bought for a Pentax spotmatic . Works great