The TT/Triathlon Dual Control Levers ST-6871 allow the rider to change gears and operate the brakes when using the TT/Triathlon extensions.
As you can read in the 6870-series manual, the handle inner diameter is Ø19.0 – 22.5mm and the handle outer diameter is Ø 22.2 – 24.0mm.
They are compatible with carbon fiber handlebars (with aluminum inserts where the brake levers are installed) or aluminum handlebars.
Note that carbon fiber handlebars without aluminum inserts (where the brake levers are installed), cannot be used.
A set of levers weighs 148g.