I got the adjustable comb when I bought my 725 but have never had to adjust it from all the way down. I bought a used 425 a with the adjustable comb and had to raise it one spacer. I bought a new BT 99 and had a Graco butpad system and the adjustable comb added aftermarket and it also need one spacer. I figured different guns may need different systems so I get the adjustable just in case I need it, if I don't well ok.