The Ultegra R8150 Rim Brake levers weigh about 295 g for a pair of levers.

They're essentially the same as the previous generation Ultegra levers, except for the fact that they'll work with the 12-speed derailleurs - using the SD300 port type.

Unfortunately, this also means that these 12-speed rim brake Di2 levers are not wireless. You can only connect them to a Di2 system using EW-SD300 wires.

12-speed rim brake shift levers have two SD300 ports and one satellite shifter port.