the neoprene gasket materials comes by the foot
You can buy the material from Pompanette which has a web site and a good customer service team. Or you can find it at reputable marine stores that know something about sailboats, not the Boaters World kindsof places -- even many of the West Marine locations will give you a blank look.I even found some on e-Bay. Buy by the foot. It's something that needs to be replaced after ngto 10 years (dependig on your conditions) so that you get that snug watertight fit when you close and tighten the dogs on your portlights.You'll have to use a screwdriver or something similar to pry out the old gasket material, clean it up as best you can and then it simply fits in the groove of the portlight. Place the longest continuous piece along the base and sides of the portlight to make sure you're not fitting separate pieces together in those places where water is most likely to accumulate and leak through. It's about 3/8 inches wide and is T-shaped. Has orange paper on the small side that you peel off as you place it in the portlight. It stopped my chronic leaks and drippings just like that!Rick