The tubing is super stiff because it is non-porous. Most silicon and other very flexible tubing actually allows water to pass through (slowly, eventually) making the system require maintenance. The tubing CoolIT uses on this is as non-porous as possible - the only thing better would be copper tubing. Once you get it installed you'll love it. I still have the test unit strapped to a Core i7 920 right now at 3.8GHz and it's running 38°C.
Enjoy!