consist of a approximately 100 mm wide break-resistant lens made of transparent, flexible polycarbonate edged in profile rubber and provided with a special soft rubber seal. To evacuate the bell jar, a freely rotatable, in any orientation sealing and thereby the workflow logically following valve with conical hose nozzle for the 1/2 "- serves vacuum hoses. On request, we also supply connection couplings instead of the conical connection. All vacuum test bells are equipped with a vacuum gauge to eliminate misjudgment due to incorrect test vacuum. The economic length is between 500 - 750 mm. Other lengths are possible on customer request.