Mesh.CombineMeshes - what happens to colliders?

Hi,

I'm combining multiple meshes into a single mesh using a custom script that also uses Unity's built in Mesh.CombineMeshes. The result is a parent object with a Mesh Filter.

I'm wondering what happens behind the scenes to the colliders that are attached to these individual meshes? Are the individual colliders simply left alone (and still behave as normal) or are they combined into 1 large mesh collider? Based on inspecting the objects at runtime it seems that each submesh still has its own collider.

The reason I ask is because I'm combining lots of cubes that all have box colliders, but don't want it to somehow create a mesh collider that will hinder performance.

This is just a sanity check really...