The BDOP DERAILLEUR CLAMP is machined from aluminium and is designed specifically to clamp on carbon tubes.
The pivot and clamping points have a machined radius so they won't concentrate pressure at very narrow points in the frame which can lead to cracks.
The BDOP DERAILLEUR CLAMP is available in 31.8 and 34.9 sizes and comes only in black.
Bicycle parts - BDOP FRONT DER CLAMP