Enlightenment of confusion:

Yes and no. This part is not intended for lamps fit in in the only 18650.
It's too thick. It does not fit into the lamp.

The cheap lamps from China, however, are intended. They can operate with such an adapter sold here and 3 AAA. You can also insert a 18650. Since this is a little thinner, it needs to a plastic tube in which the 18650 is inserted.
Usually, these lamps come with both a holder for 3 AAA as well as with the pipe.

The article sold here is thus a reserve holders for torches, which are already delivered with such holders. So you can replace all the AAA Battery Pack go.

Of course the price for this adapter is exaggerated with 5.50. If you put even 0.80 to you get the part with includierter flashlight.

So I have also made it and the part not acquired here. If you buy it, you have to make sure that it has these 5mm long and 5mm thick metal tip. Since ne feather stuck in it, so that the holder fits in in various lights. Holder without this tip does not fit anywhere in!