These Vaillant black 87 degree plume elbow are for use with a plume management kit if more bends are required.

They help direct he exhaust gases emitted from the boiler away from windows, doors, or other areas where it could be a nuisance or cause damage. By using these elbows, the installer can reroute the flue gases to a more suitable location. This helps in managing the plume and ensuring that the boiler operates efficiently and safely while complying with local regulations regarding flue gas emissions.