... which I wouldn't have had a problem with, had I not specifically asked Eleaf CS prior to ordering and been told that this battery definitely comes with the magnetic ring.
It does not... therefore be warned you won't be able to use this specific battery on its own with other tanks.

There are a few limited sellers who sell the ring separately (search 'GS Baby Magnetic Connector') but if you can't source it, the only way to use other tanks with the Pico Baby battery is to buy the complete kit.

The battery itself is decent quality. Size and shape is a clone of the Chels Microstick 18350 but with the battery capacity of a decent 18500. Build quality is fine and weight is 76.1g. Has that odd feel of raw brushed aluminium so quite grippy but lacks the solid quality of a Microstick, however I like the silver finish a lot.

The opening for the tank is 16.9mm so the 16mm Origen Tiny Tank has a little bit of rattle. A 16mm ID x 0.5mm O-Ring or some electricians tape would remedy this and also protect the acrylic tank section as there is a slight lip at the top of the tank recess. The inside of the recess is wider than the top so there's plenty of room for air circulation.
The bottom centre pin is spring loaded so in the photos below, assume that the tank would sit a couple of millimeters deeper if the magnetic base were present. Even so, pushed completely down the Origen Tiny Tank sits 3mm above the recess opening.

I can't talk about the pairing or performance because of the lack of the magnetic ring renders this useless for now.

I'll upload better photos later. It's late and I'm tired:

I'm going back to Eleaf CS about the ring in my instance. Hopefully performance will be decent. Size wise it's a good pairing with the Tiny Tank and very stealthy given my larger than average hands can completely encompass the setup.