Architect Ravenheart

I've got a question for everyone about Prim Composer in 3ds Max and I'm hoping someone can help me, I keep trying to use the "Mirror" Tool in 3ds Max, and it seemed to work perfectly if I was just working with meshes, but when I try to use it on Prim Composer objects, it doesn't mirror it - It turns it into a mini-Object and doesn't even flip it. It only does that if I try to make it work on the X, Y, or Z Axis, but if I do the XY, YZ, or XZ Axis the mirroring tool works fine. If someone could help shed some light on this, I'd really appreciate it!