While on the surface it may seem like Red Bull's 2021 challenger, the RB16B, is a carbon copy of the RB16, it is now clear that the team have overhauled their rear suspension. The suspension setup has been reversed so that now the bottom wishbone is at the rear of the framework rather than at the front. Red Bull's modification to the rear oddly mimics the setup used by Mercedes.
While there is no clear confirmation, it is highly likely that the team spent some of their development tokens to execute their modifications. Whether this will give them an added performance advantage is unclear, though with the first official test fast approaching, we will get an answer soon enough.
Check out what is different about the new Red Bull in the video via this link.