The “3” isn’t an easy connection between middles and setters, as Cary points out here. It takes a confident setter and a middle who is disciplined enough to approach to the same spot on the net every time. (Some coaches prefer the spot on the net to be determined by where the setter takes the ball, but Cary coaches her setters to adjust their sets so the MB can attack at the same place every time.)
In this video, Cary narrates as Tera and Leila demonstrate a “3” set. Tera uses a 3-step approach, and Cary offers tips about how she can coordinate her steps to come in at a better angle for more hitting options.
Hitting seam is one of the most effective attacks on a 3 set. Cary explains why in this video.