Believe it or not, this improves a great deal your antenna performances, in case you have very slow speed or connection problems at times.
Make a quick'n'dirty test by holding the antenna between your thumb and index finger (see picture).
If this improves a lot your ESP-01 performances (in my case file transfer speed got 10 times faster), then this thing should do a similar job.
Not sure what this thing actually does, maybe it somehow shortens or modifies the antenna shape...
BTW, if you are fighting with ESP-01 jumper wires, have a look at this: