Originally Posted by
purevl
The "X" series tubing, like SLX, all have "helical reinforcements" while the standard tubes do not. If you pull the bottom bracket and the seat post and shine a flashlight through the seattube you can determine if the bike is SLX or SL.
No, you can't, actually. The "helical reinforcements" got their start as a modification to the SL set when braze-on front derailleurs came into vogue. The idea is that they dissipate the heat and help prevent cooking the tube when the derailleur tab was added. So some SL sets will have them. SLX was a marketing move to take advantage of the idea by expanding it to the whole set. You'd have to check more than just the seattube to determine if the frame was actually built with SLX. I'm guessing that the OP's frame is SL - I think it's too early for SLX, and Colnago seems to have moved away from the chrome lugs when they began to distinguish the Superissimo by tubing type.