This is what Velocity says:

The Major Tom brings together everything you have been looking for when taking that next step in the cyclocross circuit. Blending qualities from our popular A23 clincher and Escape tubular rims, the 23mm wide Major Tom provides improved traction for unparalleled ground control. Designed with an 11mm braking surface for precise handling and braking, along with our seam relief channel which allows for consistent and reliable tubular tire installation. Now take your protein pills and put your helmet on!