Soft Hackle Grey - Soft Hackle. The Grey Soft Hackle fly is frequently referred to as one of the top soft hackle flies available. The neutral colourings of this fly enable it to emulate a multitude of common trout prey such as caddis flies or mayflies. This fly is known to be particularly effective on lakes during Mayfly hatches. It however can be used to target rainbow and cut throat trout with great effect.