A) Overall view of primate chair with halo device. B) Exploded view of the attachment arm (1), attachment plate (2), and halo frame with posts and skull pins (3). C) Enlarged view showing insertion path of skull pin. The pin passes through stainless steel nuts and washers (1), an aluminum offset post (2), a titanium plate that is attached to the skull with titanium cortex screws (3), and into a predrilled hole in the skull surface (4).