I use Whidden dies for my ATip 110gr-shooting 6CM. When you order the dies on the website you have three options, 1) you can use their basic stem (which is machined based on certain bullets), select from one of their bullet specific stems (not necessary if the bullet you want is used in the basic stem), or have a custom one made. I've done all three. They do a great job of keeping up with current bullet options on the market. Quick note free of charge: I still have a Hornady sizing die that I use with 6.5 CM and every time I go from that one back to the Whidden die it's like going from a Kia into an Aston. If you must stick with the Hornady sizing die, trash the sizing button/stem and run them over a mandrel. The mandrel and die will run you like $80 or something (like the one I got from LE Wilson) and it produces a much smother operation than pulling the brass over the button. But, no, Hornady is not the only maker of ATip seating stem. Though I'm not sure how many non-Hornady mfgs stems will fit Hornady dies. Just get a better die, it's w o r t h it