From the manufacturer's official website:

The Chorus™ QS™ front derailleurs in the 2007 range, in both the standard and compact crankset versions, have a longer front link to provide snappier and lighter shifting in combination with Ergopower™ QS™ controls. The cage is in aluminium with a surface treatment which exalts lightness and stiffness, with even more responsive shifting.

For double standard crankset: capacity 15 – max. chainring 54 - min. chainring 39 - light alloy fork with antifriction treatment.
Nominal weight: 74 g.

For CT™ compact crankset: capacity 16 – max. chainring 50 - min. chainring 34 - light alloy fork with antifriction treatment.
Nominal weight: 78 g.

For more information, please visit this product's webpage.