same battery code, different lengths?

Hi all, I have a few 18650 batteries now, all are protected as far as I'm aware. But a couple of them are a lot shorter even though they share the same battery code. The appear to have the 'disc' at the top which I understood to be the protection circuitry but although they're flat top, they seem to be much shorter than just the difference in the cap. Any idea why these two, which are Panasonic NCR18650B and share the same battery code on the side as all the others, would be such a difference in height? Thanks.

18650 is the nominal size for a bare, flat top cell.

Panasonic doesn't make protected cells - none of the major li-ion manufacturers (Panasonic, Sony, LG, Samsung) do - they are made by secondary companies. A giveaway for protected cells is a conductor going to the negative terminal so the protection circuit can measure cell voltage to open the positive contact in the event of over- or under-voltage.

Left to right ...

• The leftmost pair appear to be bare cells - they resemble stock photos of NCR18650B's
• The "Torchy" cells are button-top, which adds length regardless of whether or not a protection circuit is present (it's difficult to say whether the darker strip under the logo is a ground contact or a seam in the wrap)
• The rightmost cells have different positive contacts and a conspicuous external disc but also have the same outer wrap; is there an external ground contact on the backside ala this photo?

I would use heavy caution buying any "protected" Panasonic cells. I have seen way too many fakes out there. As idle points out, they never made them. Who's to say the Third Party is using genuine Panasonic cells to create these?? They likely are not. FWIW: Those green NCR shrink wrappers can be bought for pennies.
I urge you to stick to a reputable seller when buying batteries. For example: Use the Vendors on CPF.
Good Luck, and have fun!!

Thank you very much, I didn't know that you couldn't get official Panasonic protected cells.

The first pair I bought, via a recommendation on here, appear to have the metal band going to the negative terminal, as you can see here.



The Torchy batteries, a reputable seller here in the UK, seem to have the same under the wrap, as seen here



So I'm guessing that the other pair are unprotected batteries as there's no sign of that band under the shrink wrap as far as I can see. I have a good Xtar charger and they're used in lights such as my Convoy S2+ so should be ok for discharge and charge protection.

Thanks very much for the help in explaining and allowing me to ID them properly.