Shadow Rolls (or shades) are designed to prevent the horse from looking at the ground in front of him, and therefore to prevent him from looking at shadows - which can lead to shying and thus loss of gait. A properly fitted shadow roll will still allow the horse to see directly in front of him.
This model has synthetic bristles mounted onto a noseband. It is designed so that the bristles will move as the horse races, thus training the horse that it is perfectly normal to have something moving beneath their eyes. The idea is that the horse will pay less attention to shadows or any other movement on the track in front of them. It is said that this model is perfect for horses who are long or short sighted.