Vitra Tom Vac Stackable Shell Chair by Ron Arad - Set of 6White with chrome legs Tom Vac plastic shell chair designed by Ron Arad and manufactured by Vitra, Germany 1999. Tom Vac chair offers a high degree of comfort both indoors and out. With an opening at the rear, the corrugated plastic seat facilitates the stacking of up to five chairs at once. Special additives to the plastic shell prevent it from bleaching in the sun. A wonderful chair to freshen a traditional table or use in any modern installation.