Chards choker permit killer offers both bulk and a soft water entrée. When you permit fish, most of the time the fish will spook without ever seeing the fly for the first time.
A common method to make sure we show the permit the fly is to present the fly very close to it head. Well in doing so you need a fly that lands as softly as possible to help reduce the risk of spooking the fish from the fly hitting the water so close. But we still need the fly to sink like a real crab trying to flee to the bottom.
The spun deer hair head on chards choker cushions the weight of the fly hitting the water allowing a soft entrée. The Choker is also tied with heavy lead eyes to help it dive quickly to the bottom. This diving motion is what I think triggers permit to attack the fly. Looks like a crab diving quickly to the bottom to hide.
So this fly dives fast and lands soft. A deadly permit fishing combo!