In September last year, Toro Rosso announced that they would be switching engine supplier from Renault to Honda, and nearly a year later their sister team, Red Bull, made the same decision. Due to this decision, and despite Toro Rosso has made clear in the past that they are very much their own team, they have decided to increase their cooperation.
With this increased cooperation, the two teams have decided to share an entire rear end, which will include a complete gearbox and the inner parts of the front suspension. This closer partnership will mean that they will move closer to the relationship enjoyed by Ferrari and Haas, as they use all of the parts that Ferrari are legally allowed to give them.