I like harpic but this blue version has a very aggressive smell that burns the insides of your nostrils.
So, beware: use this in a wall ventilated bathroom!
Also, the blue version actually has the best consistency compared to the other toilet cleaner. Green and yellow versions there is a 4th version that I have not used, ever.
The latter two ( green and yellow) are very liquid and flow down the sides of the pot a little too fast. The slower they flow ( dense liquid, like the blue version has) , the batter. The germs must get caught and killed, as the product supposed to do. Yes, you will additionally need to brush down the sides after having let the liquid do its job for some 5-10 minutes.
This is best toilet cleaner. So I suggest you try this product.