NX 1x Rear Derailleur Dura-Ace Di2 designed for use with carbon

designed for use with carbon fiber rims

Most later Shimano derailleurs use an 11T pulley and this item would not fit those derailleurs

Revelation before model year 2009

configurable

it's too big

NX 1x Rear Derailleur Dura-Ace Di2 designed for use with carbonThe SRAM NX X HORIZON rear derailleur provides the same smooth, reliable shifting action as XX1 from the larger upper pulley offset to the 12 tooth X SYNC pulley wheels. By eliminating unwanted chain movement, X HORIZON shifts faster, puts an end to ghost shifting and reduces shift force and chain slap. And with CAGE LOCK technology, wheel removal and installation are easier than ever.