These units are outstanding- Solidly made of high quality aluminum extrusions (and made in the USA Too!), Easy to install, and easy to use.  Used together with a top stabilizer they provide a feeling of ladder security that allows me to feel comfortable atop my 24ft extension ladder for the first time. I was concerned about adding more weight (about 3-4 pounds I estimate)to my ladder, but I find that with the extra 10" of height they give, I can separate my extension ladder to give effectively a 13ft straight ladder with adjustable feet that is long enough for most jobs and only about 24 pounds. Since the feet don't interfere with the ability to recombine the ladder to the extension mode, I can do so for the few times I need to go higher. While the combined ladder is 3-4 pounds heavier, the additional safety, convenience and height is well worth the extra weight. At age 74 I finally have the best of all ladder worlds. I'm sorry I didn't buy these 30 years ago!