What are you going to use your rig for? Competition? LE duty? SHTF/Zombies?
I rock an ITW fast mag on my duty belt. I like it. Holds the mag tight, but not too tight. I will say that when I went to but a double pistol mag on top of it, I had to do some engineering.It works though.
They don't have standard size mounting for molle attachments, they are proprietary to only mount fast pistol mag pouches to them. I didn't want to use the fast pistol mag pouches. I did a little trimming and got it to work with no problems.