I wouldn’t rely much on those, honestly! Even being functional, don’t seem to be the best lights around.
It is better to start this way: what’s you budget and do you prefer “tailswitch” or “twisties”.
There are the BLF 348 clones (under different names on Gearbest and AliExpress) for clickies, and I can recommend the Nitefox K3 for twist heads (3 modes + strobe, Cool White tint). These are more reliable that those from ebay, probably, depite a bit more expensive when buying a bunch of them!