Yes, the combs are completely enclosing but not tight enough. To prevent them from slipping, I fixed the combs with a little superglue, as this bothered me a bit. If you do it carefully, you can get the combs loose again if necessary.
There are 3 fully enclosing combs on each extension cable. In addition, as shown in the picture, there are 4 more combs that are not completely enclosing.