TT / Triathlon Dual Control Lever
The TT/Triathlon Dual Control Lever ST-R8060 allows the rider to change gears and operate rim brakes when using the TT/Triathlon extensions. A pair of them weighs 138g.
An hydraulic disc version exists too, the ST-R9180 Hydraulic Disc TT lever is almost identical, except that it operates hydraulic disc brakes.
The ST-R9160 is the DURA-ACE rim brake lever. It's lighter than this by about 11g, but the functionality is the same.
Note: These shifters have one button each, so can only shift the front derailleur when used with Synchronized Shift.
These shift levers are 12-speed compatible, if you update them to firmware version 3.3.0 or newer.
These shifters have to be connected to the BT-DN300 battery by wire. They will not function if there isn't a wired connection between them and the battery.
You could plug them into one of the wireless shift levers, but they won't work unless you then connect the shift levers to the battery by wire.