This is the Minox replacement for the very very hard to find PX 27 batteries. One of the reasons is that these batteries are forbidden nowadays because of their toxic content. Obviously, there are other replacements on the market, such the famed (or less, so I have heard) Exell batteries, old stock PX27 / V27PX and others. The sealed batteries such as Exell or PX/V27PX are all right, if they're fresh which doesn't always happen, but to be honest, I always find easier to deal with the adapters. I had a few problems in the past with depleted batteries, and I renounced them altogether, never looked back.
While I do use the 8x11 Minox pack in some of my cameras, I love the adapters: easy to use, easy to replace the cells, easy to replace the entire thing, if something goes wrong with it. An adapter lets you control what happens with your camera; I always put fresh cells in mine, and always carry some spares in my bag, plus a couple of cardboard tubes, if I need an improptu adapter fashioned on the spot. If that spot is remote, well, you can see why is better to carry fresh spares with you. A few words on all these adapters and pack would not go amiss, I would say.
You will need 4 x AG12 / LR43 cells (or 2 x CR 1/3N, 3V each). No need of anything else, since the pack will do the job for you. Make sure you match the polarity of the pack with that of the cells, when you insert these in the sleeve. The sleeve itself has a metal bottom, whose main role is to get the voltage from 6V to a nominal 5.6V). Plus that it supplies the correct length for the thing to fit perfectly inside the battery chamber.