The mechanical stress caused by different expansion coefficient are absorbed by flexible neck.

A vacuum tube exposed to all weather conditions. While the ambient temperature is in sub-zero range, the condenser can experience super high temperatures (300 F). There will be always a temperature gradient between heat transfer structure and racking system. Since they are having different thermal coefficient of expansion, a mechanical stress exists between these dissimilar materials. The flexible neck system absorbs these forces.

A flexible neck system absorbs mechanical shocks.