I installed them on my H17, and I don't know how the area of deck is shaped on your NACRA, but I used ones fron Murrys with a contoured ring for curved surfaces. It worked great. I would reccomend using silicone to isntall them... is seals good and makes a good gasket, but you can get the rings off and the silicone off if you need to change them. I did this on my P16 when one cracked. Other sealants can be more perminate and make taking them apart later a real pain. Also. when you install them, only run the screws part way and let the sealant set up. Then tighten the screws later so the sealant acts like a compressed gasket. I used small SS machine bolts with backing washers and nylon locknuts not just sheet metal screws.