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 else, 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 can take smaller diameter wires, due to a smaller diameter pin that doesn’t get stuck too early. 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.