I have a Bomar NIBO acrylic hatch that I replaced last year. A heavy-weight crew member came down hard on it and split the lens. The frame (a "frosted" aluminum) is in good condition, as is all the hardware on it. I've not removed the lens so it can be used as a template. I can't bear to throw it out so I'm offering it free for the needy individual who is willing to pony up for the shipping (UPS). The cutout is 20-1/8" x 20-1/8" which allows about 1/16" clearance on each side. I used it in my cockpit floor and replaced it rather than pay what it would have cost to have new lexan put in it. I thought about replacing the lens with 3/8" Starboard but got such a good deal on the Lewmar that I couldn't pass it up. If you are interested, shoot me an email at <tkoehl2769@comcast.net> and I can send you photos as needed. -Tom