The Di2 Remote Sprinter Shifters work in conjunction the Di2 ST-7970 STI levers. There are two buttons in the set and both control the rear derailleur. One button accomplishes upshifts and the other downshifts. They can be located anywhere on the handlebar with the general ideal being to locate them on the drops so you can achieve a competitive advantage by making a split-second, critical shift while going all out in the drops.
As with the rest of the Di2 components, the construction is durable and the engineering is proven reliable. Set up is a breeze and they are a pleasure to use. These are a critical accessory for any sprinter with Di2. Package includes two remote shifters and needs a pair of Di2 STI levers to function - they will not work alone as a primary shifting unit.