I can not actually rate the usefulness of this product because I couldn't use it on my particular aero bars. I have used other products by Profile Design though and those have been great. Like I said I was unable to use these because the product could not be shortened into its most narrowest position to fit my bars. It's probably not the fault of the maker of this products it's just that my aero bars are really narrow. I do recommend this product if you know your bars aren't narrow. I can't tell you how narrow my bars are because I haven't measured them and don't have the energy to do so right now. lol.
Combined Aero HC with a Lezyne right-hand bottle cage to make an aero water bottle holder between aero-bar extensions. Had to do a little fiddling to get aero extensions close enough to fit widest adjustment of Aero HC. The centerline of the plastic "half circles" that seat against the bottom of the aero extensions is 4-1/2". This means for proper fit, your aero-bar extensions should be 4-1/2" wide, centerline to centerline of the two extensions. You can try this before you buy. Move your aero-bar extensions together so that the center of the extensions measures 4-1/2" apart. If this feels okay, you're in business.