I needed 4 mm banana plugs for my laboratory power supply, which turned out to be quite a journey. I managed to find a bunch of old Tesla WK 459 00/01/02 in my stash of socialist era parts, however their peculiar spiral-like design doesn’t seem to be gentle on sockets, they didn’t make them in black, and all of mine are very difficult to clean. I had to get something different, ideally with red, black, and green sleeves--the last one to match the battery charging socket.
On the right side of the above photo, you can see a screw-on banana plug adapter for Brymen probes. These are precisely made, durable, and make good contact.
I ordered something something vaguely similar on Aliexpress and boy, did I fail. Forget the miserable gold plating, and hard-to-screw-in pins. The springy sleeve spun around freely, and barely made any contact at all!
Luckily, not all was lost and I’ve managed to make them useful with a bit of soldering, like someone hinted at in their review. At first I tried a soldering gun, the result of which can be seen here, however that left a lot of hard-to-remove resin on the part, and it’s easy to mistakenly touch undesired areas. It turned out that it’s easiest to just heat up all plugs with a hot air gun, and apply rosin core solder directly, with no additional flux.
They’re still mediocre, but at least I don’t need to throw them out, and can use them for disposable cables. Apparently they’re just bad clones of something that’s not so spectacular in the first place.
Before I mustered enough willpower for the aforementioned adjustment, I remembered that there was this entirely different kind of plug that I don’t exactly know how to call, and I ordered two sets from different sellers. Guess what, they’re slightly different! See if you can spot it on the first photo. One of those can take smaller diameter wires, due to a smaller diameter pin that doesn’t get stuck too early. Anyway, they seem to be fairly solid, and the best Aliexpress has to offer, although, again, it looks like they might be a bit hard on sockets.
Interestingly enough, the same rubber sleeves are used as for the more banana-like plugs.
Later I’ve found Jiří Bekr's video reviewing various connectors. I wish I had discovered it sooner.