This is the very best especially with extruded powder:
http://www.neiljones.com/html/measure.html
They hold the tolerances so close that most of the competitive shooters I was around exchanged load data in clicks of their Neil Jones measures.
But I own Harrell's Premium and Shutzen/Pistol powder measures to cover everything. I also have a Belding & Mull for hunting loads to get close and trickle up.