Specification The ideal solution for many cameras such as the Olympus 35EC, Yashica Lynx etc that used the original PX640 (1.35V) battery. There is an equivalent PX640 which is available today - it is the same size and shape as original, but the voltage is now 1.5v instead of 1.35v. There are two issues with this: 1). The over voltage will give inaccurate meter readings, and over time can burn the meter cells. 2). It is not cheap. One battery is approx 6.00, and once the power is used - throw it away. So is there another solution? Yes - fit this adapter (which is the same shape as the PX640 battery) into the battery terminal of your camera and power it using a "Zinc Air 1.4v battery" - the good news is the 1.4v Zinc air battery (which is shaped like a standard LR44 battery) can be bought for around 50p - so it is a great saving if you use your cameras often. The zinc air battery are known as 675 battery (aka: hearing aid batteries) The adapter is precision made. The design may vary slightly Please note: the listing is just for the adapter only - the "1.4v zinc air batteries" can be found online from a number of sources Q: Will this convert the voltage of a battery? A: No - the adapter will not convert a voltage - it only converts the physical size of the battery Q: So how does this work? A: Simply place the copper adapter into the battery terminal of camera, and insert one 1.4v zinc air battery into the holder. Q: So what battery do I need? A: You will require a Zinc Air 1.4v battery - which is known as a 675 (often referred as a hearing aid battery). They cost around 50p Q: will I need one or two adapters? A: depending on you camera, you may need two adapters Q: there are others on eBay at a cheaper price - why is yours more? A: be wary of some being sold on eBay. They do not have air holes. Zinc air batteries require air circulation to activate them (hence zinc air). The other units on eBay are simply a piece of metal to accommodate a standard 1.5v LR44 battery. Although it will power the camera, it will not give accurate readings (so back to original issue), Quantity: Copper Made PX640 HM-N Camera Battery Adapter for Vintage Film Cameras This PX640 battery adapter that allows the use of a zine-air cell in vintage cameras compatible with PX640. Tips: Please allow 1-3cm error of measurement. Photo color might be a little different from the actual product due to color display of different monitors. Product Includes: 1X Copper Made PX640 HM-N Camera Battery Adapter for Vintage Film Cameras