The 7900 front mech, along with the front shifter that controls it, has a different cable pull ratio to any other Shimano front mech, so they only work together – so no mixing and matching of parts allowed. It works great though.
There’s no need to have a trimming step in the shifter throw any more, as when set up correctly this front mech can handle any combination of front to rear gear choice without a hint of chain rub.
It's a wonderful bit of design, and with cold-forged alloy construction for the main body parts and nickel-plated aluminium alloy plates this is a fantastic, stiff front mech.
It works with standard and compact chainrings (50t to 56t top gear max with a capacity of 16t) and comes in both braze-on and clamp-on designs for three seat tube diameters – 28.6/31.8/34.9mm. Both options are individually designed. Weight is 64g.