The ShockStop Stem fits all standard 1-1/8 inch (28.6mm) steerer tubes. Some newer versions of the Specialized Sirrus Sport and Sport Carbon have integrated stems and headset spacers (see the picture below). 

The ShockStop Stem will still fit your bike, but you will need to buy a standard steerer tube top cap, and you may need to replace the integrated steerer tube spacers with standard round ones (otherwise the spacers may look a bit strange since they won't match the profile of the stem). 

Both steerer tube cap and spacers are readily available at any bike shop, and should not cost more than a few dollars for all of the parts you need.

Tags: Specialized Sirrus Sport Carbon, Specialized Flowset stem integrated