Volumizers can help to lower pressure on the LED, and are necessary for lowest pressure operation on the Speed and new A4. However, on the LCD and IR3 they add so little extra volume that they're basically useless (as far as functionality is concerned). But, they look pretty bling on certain models (I put two System X's on my Rock IR3, and they add quite a bit to the looks). In the LED, LCD and IR3 only one volumizer is functional, as only one side (the right) of the marker houses the LPR. But in the Speed (don't know about the A4) the battery is smaller, occupying only about half of the left tube of the marker, and the LPR is housed in the left side, leaving the entire right side as a huge air reservoir, so dually's might actually have some purpose on them.