How to set a "fake" size for an object?

I have a MeshPart with a size (2.42, 0.848, 1.334).
But for collisions, I want this mesh to like inside an “invisible” box with size (4, 4, 4).
Is it possible?

Place an invisible part around it

You could try making the part you want to be seen as a part with the property CanCollide set to false. Then for the collisions, you could make a separate part with CanCollide set to true. If you don’t want the part to be seen, you can just make it invisible with the Transparency set to 1.

Make a new part around it with size 4, 4, 4. Set the new parts transparency to 1 so it’s invisible and set the MeshPart’s CanCollide to false.

If you need the MeshPart to move, you can weld the invisible part to the MeshPart so they stay together.

I know that @Fire540Games already answered, but you can do this easier.

Just add a part to workspace with the size 4, 4, 4, then under the Properties tab on your mesh (make sure it’s under the part), set the Scale of the MeshPart to something like 3.5, 3.5, 3.5, or your desirable size. Then, as long has you have CanCollide on, the mesh will appear as if there is an invisible box around it.