Professional bass fishing started and flourished in the U.S. But nowadays, thanks to introduction or "invasion" of the mighty species, black bass, many anglers in other countries also enjoy bass fishing. In Korea, bass was intentionally introduced by the government to its waters as a potential protein source in the 1970s. Now, although they are considered as invasive species, as are Asian carp in the US, many sportfishermen enjoy bass fishing in Korea. They are also developing new techniques and lures, which can be referred by American anglers in reverse. This is a good thing.
I saw a post about so called, "monster (flex) jig" at a Korean lure makers' website, http://goldworm.net, which I thought brilliant. Basic idea is to separate sinker and hook parts of jig head, and link them with a split shot. This makes it easier to customize presentation and give more erratic action. You can find pictured tutorial of monster jig making, which was presented by Jinchoong Kim (Sorry, it is written in Korean, but you still can look at the pictures.). Here I put only a few pictures to give you some idea about the monster jig.
This was originally developed by a professional bass angler, Jae Bum Park, who is a member of Korea Sportfishing Association. Here is a link to his blog post about the monster jig (in Korean). Recently, this jig was commercialized by Sure Catch Korea (also in Korean).
I did some web search using key words, 'monster jig' and 'flex jig,' and found that Hogie's has a similar product called flex jig. This jig head is for salt water fishing, but I could not find further information about how this is rigged. It seems that they do not put skirt on it. When I find cool products and tactics developed in Korea, I will introduce them here.