A system, method and an end effector may arrange into a group two articles within a stream of articles moving spaced apart and in a line in a conveying direction on a conveyor. The system, method, and end effector may contact and slow the more downstream of the two articles and then contact the more upstream of the two articles without substantially slowing the more upstream article to form the group. The end effector may include a downstream stop portion for contacting at least one of the articles.