This stuff is very like the product I use to descale my plastic kettle, but more gloopy. Rather like the old Gloy, in fact! You unscrew the cap, which has a stubby brush attached. Wipe the stuff around tricky places, eg the tip of a tap which has limescale on, leave it for 20 mins or so, rinse off and presto! no more limescale. Also great around the seating of taps or the edges of plugholes. Be careful with enamel, but it is ok on stainless steel, plastic and ceramic.