Metal bellows mechanical seals Features:
It's Composition of A Seal ring (moving or stationary) and a bellows,has no Auxiliary ring in between, so decrease a Leak path.
All together,It decrease the friction drag.
Welded metal bellows seal for the temperature limit is not supporting ring.
PTFE bellows seal can be used in corrosive liquids.
But Some Metal bellows mechanical seals has not enough bounces,need to add the Auxiliary Springs.

Typical applications include: cryogenics, heat transfer fluids, severe chemicals and corrosives at temperatures from -350° to +650°F (-212° to +343.33°C) with standard seal construction.