Here you can find something related to ASME-PVHO approved viewports. http://www.hyperbar.com/windows.htm -- Paolo Velcich industrial designer ******************************* KORUM DESIGN Viale Tricesimo 5/6 33100 - UDINE - ITALY Tel. (+39)0348-2611707 e-mail: pavel@mail.nauta.it http://nauta.com http://www.polarexpeditions.org *******************************