"Did quite well on very tough spot - shower hose"
I have a metallic shower hose that you can't disconnect from the shower and it's one of those slightly stretchy ones where limescale builds between the grooves on the hose. Nothing would shift it. Put the gel on and left for a while, then put old toothbrush head on electric toothbrush and worked on each grove. Started to shift it, reapplied and a bit more went. Better than anything else but not miraculous as it wouldn't budge without the extra help from the electric toothbrush and didn't manage to budge all of it. A painstaking work in progress but better than nothing!