This is a popular deep water rig in the Gulf of Mexico when fishing in water 150 feet and deeper.  We may be looking for big grouper but we don't want to miss out on some smaller red snapper.  We bait one hook with a large live bait and the other with cut bait or shrimp.  Two live baits do not work well on the same line.  A 3/0 hook is good for school snapper and an extra strong 6/0 to 8/0 hook for grouper will work most of the time.  I like Tuna style hooks.

The Extra heavy leader can be from 80# to 200# test mono, light leader would be from 40# to 60# test mono and the extra light leader should be no more then 25# test.  The extra light leader on the lead is so that if you snag the bottom you can break it off and not lose your rig or fish.

The length of your hook leader should be no longer then the distance between the 3-way swivels.  The total length of the first two sections of heavy leader should be between 48"-72" and the extra light lead leader about 12".
Examples Length Pound /Test
First section heavy leader 24" 150
Second section heavy leader: 36" 150
Small hook leader: 18" 60
Big hook leader: 30" 150
Extra light leader for lead: 12"  25
Lead weight   16 oz.

This kind of fishing is normally done with 4/0 or 6/0 reels and 50# to 80# test line.  Make sure you use extra strong swivels!