We replaced our original Dometic-Seitz CampLite kitchen window on our 2013 11FK with a Tern Overland 300x500mm - Classic Arctic Tern Window. The wall thickness is 30mm. Thanks to the previous posts! We lost our Dometic glazing panel on our last trip. We think we're always being so careful. Sigh. The Arctic Tern fit perfectly into the rough opening without any modification. Easy to install. For now, we left the Dometic hinge profile piece attached to the trailer rather than deal with the screw holes. The Tern Overland shade assembly is slightly smaller than the Seitz blind, so we have some screw holes to deal with on the inside. Looks good too.