To install a Gruber you will need a seat tube that is at least 31.6mm wide and many carbon fiber frames may not be strong enough to use this kind of system unless the bottom bracket is reinforced. Carbon Fiber tends to fail pretty catastrophically which can be fun for the rider and any bystanders. For normal aluminum and steel framed bikes you will need to drill a hole through the top of the bottom bracket which can be a little tricky. I suggest that you use a normal titanium drill with a 2ft drill extension (check on ebay) and then something like a PVC pipe around the outside of the drill to keep it centered. Doing it this way you should be able to patiently drill through the top of the bottom bracket without destroying the frame too badly.