12 On the right is the 4R100 Low-gear drum and is required because CK Performance utilizes a six-pinion planetary. The six-pinion planetary will take any abuse you can throw at it, but won't fit in the stock C6 drum. Another advantage is that the 4R100 drum weighs 3-1/2 pounds and the C6 one is 5 pounds. The Low-gear drum is stationary in First gear, but rotates in Second and Third gears. Saving 1-1/2 pounds in rotating weight is a huge performance advantage.