imported mesh collider won't line up with original mesh

I’m trying to export just an arm from a figure mesh so I can use it as an accurate collider on the figure arm as it moves around. Right now it seems to be importing the wrong size and offset to correctly line up with the actual figure arm. I’m going from a 3d program exporting to collada ->converting to arm.fbx. Then I’m going to the bone called arm and creating a meshcollider and assigning it to the arm.fbx mesh.

Seems like if I export it correctly it should show up in the same position as the original.
What could cause it to not line up correctly. What settings should I watch out for in the during export or import?

Is it skinned or rigid mesh?

Why are you converting collada to fbx? - Unity can import collada files.

Why are you assigning MeshCollider? Unity can generate colliders for you for imported meshes, in that case everything should line up. If you’re doing it manually then I guess your GlobalScale doesn’t match and you need to adjust offsets yourself or something like that.

In “Mesh Colider” component just change “size” vectors (x, y, z).