Red Bull are making the swtich to Honda as their power unit supplier after its junior team impressed last campaign with the Japanese manufacturer.
Toro Rosso have usually used the gearbox and internals from Red Bull, however, a different casing because it has not been able to finalise and sign off its gearbox and rear suspension.
With Red Bull and Toro Rosso both using Honda next season, both teams will share a complete rear end - which includes rear suspension and some front suspension parts.
"I think it's a big advantage," Toyoharu Tanabe, Honda's technical director admitted to Autosport. "We don't need to communicate between one team and another team, or they ask us completely separately.
"We don't have that situation. Of course, they have slightly different design and we need to adapt to each team but it's not a big specification change."
Honda have not supplied two teams at once since its return to the grid back in 2015.