MT,
You can basically see the rig setup on the package
The slip bobber freely slides on your line & will sit right on top of your split shots when casting, while the bobberstop will have been reeled in onto your spool....when you cast out, your line will drop in the water until the bobber with the bead on top is stopped by the thread(in Karack's case, the rubberband replaces the thread & the bead). As long as the tied on rubber band, or the thread, are small enough to pass thru the smallest eyelet of your rod, you can use this setup in as deep a situation as you'd like, instead of having a fixed bobber on your line which you could only have set to a depth of maybe 5 or 6 feet at the most.
The slip bobber & bobberstop just make this rig castable & much more adjustable to deeper depths, as opposed to a fixed bobber which is a hassle to use & cast.
PK
p.s. MT, the black plasic tube holding the knotted thread just allows you to slide the thread onto your line, but is then removed so you can tighten the knot on your line.....you can just buy the thread and beads yourself, & use cut up straws to tie your own onto....but elastics sound real easy & cheap too!!