This is a cover for the optional Bambu Lab Anti-Vibration Feet. The covers will constrict the Anti-Vibration feet from oscillating excessively (swaying side to side). There will still be a significant amount of oscillation, but it should be reduced by 30-40%. Additionally, the covers actually support the silicone flexible feet better and give the printer additional table clearance by allowing the feet to stay more upright.

You can play with the heights to fine tune the silicone feet to your liking. Longer will limit the swaying movement, but increase the vibration, shorter will increase the swaying movement but decrease the vibration. These are set to 12 mm tall on this model. You should be able to scale the Z axis in your slicer without hurting the fit.

Also note, I suggest using a single drop of super glue on the optional Bambu feet where they touch the printer (not on my model, but the silicone feet where they touch the printer). This will keep them attached to the printer when you move it around, but still be very easy to remove. This model grips the silicone fairly well and shouldn't need glue.

P.S.

One other benefit, with these on you can slide the printer on the desktop without collapsing or rolling the optional feet off (not possible with the Bambu Anti-Vibration Feet alone).