The main reason DLD Blasters deliver such great length gains is because I invented them...duh!

Just Jokes
Blasters use 4 movements that work together. The first is the actual stretch position. The A-Stretch, the stretching position used in Blasters, gives two stress points on the shaft that are working against each other. The point where the penis is stretched over the wrist is forcing the lower portion of the shaft upwards, this stretch alone is very powerful but when we add the second point of stress, where the leading hand, at the upper shaft, is pulling the penis downward, the stretch become twice as powerful. We can consider this the "work"
In the laws of physics, work = force x distance. so when force and distance are working against each other in opposite directions the result would be doubled. This makes the A-Stretch very effective. There is 2 additional factors, being kegels and reverse kegels, that make the Blasters even more powerful. It could almost be written as W = F squared x D
When you do a kegel while stretching your penis outward you can feel a resistance against the stretch. With each kegel you do you exhausting the PC muscles. The reason this is important is because the pelvic floor muscles have a natural reflex to possible injury and stretching the penis is unnatural to the way the penis behaves. Almost like blinking your eyes when a something is coming at your face, it is a uncontrollable, natural reflex to avoid injury. This is a wonderful reflex most of the time but in stretching the penis it prevents you from full stretching potential. The reason you want to exhaust the PC muscles is that they interfere with your stretching of the suspensory ligaments. The PC muscles literally work against your stretch. Once these muscles are weak and exhausted the reverse kegel allowing a direct stretch to the ligaments, essentially circumventing the PC muscles. At this point in the exercise all components work together to deliver the best possible manual stretch.
In the case of a "Bundled Blasters" a 5th component is at work, the twist of the shaft. The actual physics and math to this is complex but if you really want it I will post it. In the most basic way, you can understand the bundle like a wet towel (do the experiment and you will see the results.) If you take a wet towel that is, say, 5 feet long and you wring it out but at the same time you are twisting it to release the water you are stretching in in opposite directing the towel will become longer. Of course the penis is much different and biological components make it a far stretch

from this example you can still make the basic correlation. It allows the Blasters to become even more powerful. If you want to be a nerd like me you can read about the elastic theory which will help you better understand this.
Between the two versions of the Blasters, the Bundled Blasters are more effective due to the twist.
I hope that answered your question and did not confuse the issue.
DLD