If you wish to see the full specs then see the links on the Previous Page which lead to their individual page and more info at Global Win. Basically the Tak68 has 2 fans on each side rated at 4700rpm which pushes 23.3cfm at 36dba. The Cak-II 68 has one of the exact same fans on the Tak68 while the Cak-II 16 has a temperature-controlled fan which according to Global Wins site will generate 2800 - 5600rpms and from 12.44 - 26.36cfm at 24 - 37dba. Below is a picture of the sensor which as you see is placed at the bottom of the fan.

Below for comparison we have the fan off the Cak-II 16 to the left and to the right the fan on the Cak-II 68 and one on each side of the Tak68. Big size difference isn't it. Going by just the looks you'd assume the fan on the left would put out almost double the air delivery than the much thinner fan on the right. Amazingly that is not the case at all. At it's top rated speed the larger bests the thinner one by just over 3cfm! According to Global Wins ratings.

Below we compare the size with the Tak68 on the left and the Cak-II 16/68 on the right. *Note: The Cak-II 16 and the Cak-II 68 use the exact same heatsink, only difference is the fan. In fact they also use the exact same heatsink as their top-of-the-line Cak-II 38. The Cak-II 38 uses one of those screamer fans best left to mowing your lawn.