rigidbody stop interacting with eachother

so I have 2 cubes with a mass of 1000 so that the player can barely push them while still have a nice amount of gravity, however the cubes can still push eachother, What I want is that every object under the same tag dont interact with eachother, in other words I want those cubes to not be able to push eachother.

Is there a way to do this?

 

In your OnCollision* calls you can check against the tags and ignore the collision (IIRC)

Or you can set them on their own layer and have them interact with other layers but not their own.

 

so I tried it with the Physic Matrix tab, but now they move through eachother, the collision still needs to work and I still need to be able to stack them