The PAPAILIAS, Inc., Series RS-OB 4" x 18" ob-round view weld pad style sight glasses are manufactured from ASME Section VIII acceptable metals. The lower flange can be supplied thicker if required to reinforce the vessel opening or curved to match the vessel's geometry. Standard lengths are listed with special sizes quoted upon request. The Series RS-OB is recommended for pressures up to 150 PSIG (14.3 Barg) and temperatures to 500ºF (260ºC). Higher temperatures and pressures available with special gasket and lens materials. ASME code calculations and any resulting additional material needed to reinforce sight glass opening to meet ASME code is the responsibility of the buyer.