Frame size 52. I have size 54a in Trek so quite large in frame sizes. Cannondale SystemSix Hi-MOD Ultegra Di2 highlights: - According to tests, the world's fastest road bike - NEW Shimano Di2 Ultegra 12-speed electronic shifting group - Shimano Ultegra reliable hydraulic disc brakes - Room for tire width up to 30mm, on an aero bike! - Integrated cable routing for maximum aerodynamics - Vittoria Pro Rubino Speed tires with very low rolling resistance - 64mm high KNØT carbon wheels, developed in a wind tunnel and at the same time very reliable. And they're not bad looking either! Cannondale SystemSix HI-MOD Ultegra Di2 | Stealth Grey - The world's fastest road bike Cannondale SystemSix is, according to Cannondale's tests, the fastest UCI-approved bike on the market, and after putting lots of miles on the SystemSix ourselves, we're prepared to agree. As the name suggests, the development team worked to optimize the six most important parts of the bike - frame, fork, seatpost, handlebars, stem and wheels - to achieve the goal of building the fastest road bike in the world. After a lot of wind tunnel testing, it was found that up to 6% gradient, the SystemSix is faster than any other standard road bike on the market. This means that despite being an aero bike, it is still faster than the fastest standard road bikes (which are often a little lighter) even uphill on all slopes up to 6%. If we then look at what the terrain looks like in Sweden, you realize that for most of us it is a very small part of the time we sit on the bike that the surface slopes more than 6% uphill, which makes SystemSix the obvious choice for many. Add a little headwind, and the benefits of the SystemSix's outstanding aerodynamics quickly add up! The frame of the Cannondale SystemSix Hi-Mod Ultegra Di2 is made from Cannondale's finest Hi-MOD carbon fiber, which is both lighter and stiffer than the standard BallisTec Carbon frame. On top of that, it's geometrically as aerodynamic as a frame can get. After all the wind tunnel hours, the bike has been given a wider front fork to allow for wider tires but also to provide better airflow. The KNØT 60 rims are a good width, 60mm high and shod with 25mm tires which has been tested as the fastest possible combination for this bike. The aerodynamically designed seatpost together with the seat tube is adapted to bring the rear wheel as far forward as possible and provide a short chainstay. To this has been added a modern integrated Cockpit and aero handlebar from KNØT which, in addition to a clean look, provides very low air resistance without visible wires or brake hoses.Cannondale SystemSix Hi-Mod Ultegra Di2 is equipped with really nice components throughout in the form of, among other things, brand new Shimano Ultegra Di2 gear group. This means the latest of the latest, with 2x12 electronic gears with that great race feeling and minimal maintenance.