My Lee 3-die rifle sets come with a full-length die, a collet neck-size die and a seating die.
That is exactly what the 3 die Lee sets for 223 at Midway have. Chances are you will never use the collet neck-size die when loading for an AR. But buy what you like. But the collet neck-size die isn't going to provide any crimp after you seat the bullet as was suggested.