Specialized say:

The Rib Cage II is not only a sleek, lightweight water bottle cage, but it's also been designed to be fast in the wind. Of course, it also performs its primary task of holding tight to bottles dutifully, so you won't be losing bottles when the road gets rough.

• SWAT™-compatible design allows for storage and tool integration.
• Super-low bottle position improves the aerodynamic profile.
• Tuned compression design provides a secure bottle retention with easy in-and-out accessibility.
• Reinforced composite material improves durability without adding weight.
• Sleek, minimalist design with razor-sharp graphics.
• Accepts EMT Cage Mount MTB or Road Tool.
• Accepts MTB XC Box (when used on compatible frames).
• Weight: 33g