I saw Flex Tape advertised on television and I figured, okay, maybe that's what I can use to patch the black water tank in my RV when it caught a rock. It seems to stick to everything; scissors, razor, knife, shirt, and beard hair, but it does not stick to my black water tank. I sanded the area with 80 grit, washed it down with methyl ethyl ketone, and figured it was a clean area, but it doesn't stick.
I call the company to make a complaint but got the runaround. I finally got a supervisor, and they told me my mistake was I was using MEK to clean the area, but that's what they recommend to remove it with. I need to wash the area off with soap and water and dry it to get all the MEK off it. We had words, and none of them are any good. I think she finally hung up on me while I was busy explaining to her that MEK evaporates.
Flex Tape is absolutely useless. And as far as Flex Seal in the spray can that runs about 15 bucks a can, go out and buy Rust-Oleum undercoating. It's the same product but is five bucks a can. Flex Seal is a rip-off, Flex Tape is a ripoff.
Bottom Line: No, I would not recommend this to a friend