This is a tube style fly that imitates a mouse. It's DEADLY because like a mouse the buoyant head stays above water and the rabbit strips and spun hair hang lower in the water like the body of a mouse.
We have caught some of our largest trout in remote Alaska and Kamchatka on this pattern. We've heard it works well at night for Largemouth Bass as well.
Purchase some Gamakatsu Hooks #4 or #2 to use with this fly. Setting it up is EASY. Just thread the fly onto your leader, tie the fly on, seat the hook at the back end of the mouse to insure perfect hookups. This also insures you can put a sharp new hook on this fly as well.
As you can see by the photo, the mouse pattern will slide up the line away from the fish, helping you land fish and it also makes hook removal easy.