Hi Mike
Pretty simple. How far can you cast a live bait. 20 maybe 30 metres, and then they can swim anywhere.
Using these things enables me to put a live bait 125 to 170m off the beach or rocks into deep water as I only have to cast a grapnel sinker. We use Namix or Gemini Breakaway sinkers.
Because of bait sliders design the bait cant swim back towards you unless its strong enough to lift the sinker and bring it back to you.
If you rig the bait up on a short leader, I use 30 to 45cms, which makes the bait easier for a Jewie or King to catch as it doesn't have to chase it all over the place.