A damper is provided for responding to relative movement of arms to which the damper is coupled. The damper includes a member, springs, a first housing and a second housing. The first housing includes a first body and first bellows affixed to the member and the first body by first joints to define a first interior. The second housing includes a second body and second bellows affixed to the member and the second body by second joints to define a second interior. The first and second interiors are configured to contain fluid charged therein and the member is configured to permit bi-directional flows of the fluid between the first and second interiors responsive to the relative movement of the arms and in opposition to an elasticity of the springs.