Glass window diameter:approx.12.3in Diameter open window:approx.13.2in Tempered glass thickness:approx.4mm/0.2in Porthole overall size:approx.15-3/4in x 7-7/8in Boat porthole material:tempered glass+ABS+316 stainless steel Rubber seal ensures weatherproofing when mounted on vertical surfaces Low profile hatch designed for installation on internal or external flat surface Deck hatch easy to install,pre-drilled countersunk fastening holes (screws not included) Hatch porthole with two fittings can be loosened to allow you to swing open the porthole Package 2 x Boat Yacht Rectangle Opening Portlight Porthole ( 15-3/4" x 7-7/8" )