There has been a whole lot of buzz going around about these tires since their arrival on the market - they are lightweight, durable, roll fast and stick like glue. All the things you are looking for in a high-end performance tire.
The first thing you will notice with the Ultremo is the lack of rolling resistance and incredible grip. This is due to Schwalbe's Triple Star Compound. It has a harder density rubber in the center for effortless rolling with little to no resistance. This tread is sandwiched on each side with sticky rubber that really hugs the road. The lightness of the tire (189 grams) combined with the lack of rolling resistance and pure grip makes a massive difference and will become apparent from your first pedal stroke. They will actually improve the way your bike handles.
Protection from the elements and debris are taken care of by HD Speed Guard strip under the tread. The strip does an excellent job of preventing flats, but also doesn't impact performance. The strip is pliant and bends and flexes with the tire carcass so it will not impede with the tire contact as it contours to the pavement. Many manufacturers use a Kevlar strip or other stiff materials which tend to make the tire less responsive and decrease grip. The HD Speed does it job buy protecting the tire but not affecting the ride quality. There is some added material to the side walls to reduce sidewall flex for a more protection and secure feel.
The tire designers at Schwalbe claims " the Ultremo is the pinnacle of our ambition" and we can see why, it is one of the finest clinchers available. They are available in 23mm width in a range of colors.