Fluorocarbon has basically the same refractive index as water, which means it's much harder for the fish to detect. It is also much more abrasion resistant than standard mono. Favorite of many professionals! Please also note that it has a natural tendency to sink so it is really best viewed as a wet fly/streamer tippet. Also great for shock tippets in the salt. Everyone has their favorite...with the Seaguar being the best selling, but be sure to compare the value of the Orvis Mirage....it's a good deal.
Our favorite fluorocarbon leader and tippet materials are listed here!