Dual extrusion - object added

Hi, I have installed dual extruder in my SM2 a350. In Luban as soon as i add a left extruder part (1) in place (2) suddenly a gray tube/cylinder gets added (3) in the print area
What is it?

This is the prime tower. Nozzles uses this after color swap to clean themselves before printing.

Costs some material, but improves the result.