a in a second orientation according to a preferred embodiment of the present invention the longitudinal axis 1002 of the irregular ball 118 is rotated twenty degrees about the y axis making an angle u03b2 seventy degrees with the x axis as sections 126 128 and semi spherical end piece 604 are solids of rotation and as socket inner surfaces 902 904 and 906 are all surfaces of rotation the engagement of sections 126 128 and semi spherical end piece 604 of irregular ball 118 with surfaces 902 904 and 906 of socket 120 are similar to those for fig1 c except for a rotation about the y axis in this case fig1 d is a side elevation cross sectional view illustrating an exemplary embodiment of the restricted ball and socket joint for headset ear cup 100 of fig1 a in a third orientation according to a preferred embodiment of the present invention the longitudinal axis 1002 of the irregular ball 118 is rotated twenty degrees about the y axis making an angle u03b3 one hundred and ten degrees with the x axis as sections 126 128 and semi spherical end piece 604 are solids of rotation and as socket inner surfaces 902 904 and 906 are all surfaces of rotation the engagement of sections 126 128 and semi spherical end piece 604 of irregular ball 118 with surfaces 902 904 and.