In water which is over a metre deep, these will help to get your fly down to the fish when you are using floating lines. For bonefish you will never need to use sinking leader connectors. Fishtec and Sportfish sell mixed packets of leader connectors in different sink rates and they are a good investment.

For leaders, Matt Hayes recommends fluorocarbon for bonefish. Fluorocarbon is less visible to fish in clear water, sinks a little faster than mono and is slightly stiffer, giving a better 'turnover.' You can use ordinary mono for bonefish and if you do you will not be severely disadvantaged; choose a 'stiffish,' clear mono. For bonefish, leaders between eight and twelve pounds are ideal. The fish in Cuba are not generally leader shy.
For permit, fluorocarbon is also a good choice in either twelve or fifteen pounds. Make your leaders around the length of the rod and certainly no longer than twelve feet for bonefish and permit. The windier the day, the shorter the leader is the golden rule.

A useful alternative are the tapered bonefish and permit leaders now produced by a number of companies. They turn over nicely and are a good investment. For tarpon, snook and jacks, traditional mono can be used to create composite leaders by knotting together around seven or eight feet of sixteen or twenty pounds nylon with a short rubbing tippet between sixty and eighty pounds. You can, however, buy ready-made leaders for tarpon and they are very useful if you are not sure about how to make saltwater leaders for the heavyweights. With tarpon, you must use a rubbing tippet of heavy mono because the fish will either rub through lesser tippets or break them when they make one of their spectacular jumps.
Barracuda and sharks require a similar arrangement but with a short wire tippet in place of the heavy mono. Ready-made leaders for 'cuda and sharks are available if you are unsure about how to construct them.