There's nothing like this product.  I use it for sealing rv seams. Don't use the 4200 for boat or rv repairs. It came up after 6 months & I had to redo all of them with 5200. This was a lot of work. I've used sealants for decades. This one blew my mind & was the answer to those serious needs & ended the better-quality product seeking I was forced into for years. It probably isn't the best idea to use it around windows though, where you may need to take the repair job up ever again to change glass out. It is so good, and maintains flex so well, but removing it can be a big undertaking due to it's great permanent sealing. I tell everyone about this product. Everywhere I've found people talking about repair jobs then I tell them & a number of them have gotten the product. I just got it for a retired police officer to repair his rv. I got it on amazon.com & it came very quickly in the mail.  The price through Wesson was very good. I emailed Wesson & asked if they'd keep more available on Amazon, because it isn't always easy to find the 5200. A very good price was offered on Amazon. I was real glad to see it there.