Poly Welder Pro Polyethylene Welding Strips – 5-feet (Black)The product I purchased was the black LDPE strips not the green or white. I have an older motorhome with black low density polyethylene holding tanks for both the black and grey water. The whole key to successfully plastic welding any of these tanks is finding out what the tanks are made of. In most cases the recycling symbol on the tank, usually a triangle with a number, will indicate what it is made of. In order to successfully weld plastic you must use a welding rod of either the same density as the tank, or welding rod of a lower density than the tank. In my case LDPE worked perfectly. Both tanks had stress cracks in multiple places from the metal bars and bolts that were used to bolt the tanks up to the floor of the motorhome. I did not remove the tanks when doing this. Both of these tanks were bone dry when I did the welding. First I tried using a very small triangular shaped iron to do it but it did not get hot enough to melt the plastic to a state of flow. At that point I just grabbed my propane torch, set it to approximately a 0.5 inch or shorter flame and applied it to both the tank and the rod at the same time. You can see the plastic melt both surfaces and they effectively became one solid piece of plastic. Grab the flat welding rod several inches above the end of it and apply a bend to it trying to flatten it out to the surface of the tank. Put the flame right where the 2 surfaces meet and it will become evident that they are melting together. Be light with the flame. If you hold it too long to that area you could melt it more than you need to. This also will become self-evident. You will become better at this type of welding quickly as you do it. The results were phenomenal. No leaks at all. Tested by filling both tanks up with water as the motorhome sat on our concrete driveway. The additional material that I added to the tanks seemed to increase the strength of the tank by making the tank thicker in that area. I don’t anticipate ever having to do this again. It sure worked like a charm.