Like Larry says, Sunbrella recommends 303 and I used it with good results. Unfortunately, our bimini is now 9 years old and not even 303 keeps the water out anymore. It's kinda expensive and I couldn't justify the expense on fabric that won't be around much longer so I used Thompsons. It's way cheap and it does work. Last time we put it on with a roller because our bimini is so large (Thompsons says don't do that.) It worked fine. It does darken the fabric a bit but I don't care. I wouldn't recommend it for newer fabric and I'm sure it voids whatever warranty there might be but we don't care.