C4s are building your rack essentials.
A little bit on a heavy side compared with DMM Dragons and much heavier then Metolius Ultralight Power Cams. And more versatile. It's a trade off - weight or versatility. When building my rack I choose versatility first. Special features (like Dragon's extendable sling or Power Cam's weight saving) are to be considered when extending existing rack.
For sizes smaller then #.75 green I would choose Metolius Master Cams up to #3 orange. For #.75 and bigger sizes you can't go wrong with C4s. Consider DMM Dragon Cams as an option.