A standard installation requires a depth between 80 and 108 mm to the front face of the tile, which is indicated on the outside of the iBox as a guide. An example of tolerance issues is having to pack out the tiles more than you thought to get the wall straight but the tiling ends up being over the maximum depth to install the iBox.
To resolve this issue, you don't have to take the iBox out to move it within its tolerance, we have a spacing block that measures 25 mm in depth which will add 25mm onto the maximum line shown on the sticker guide located on the iBox. The spacing block is installed between the iBox and the brass valve.
The second part is if the wall is too thin and you are struggling to get the front face of the tile within the tolerances. For this we have a spacer measuring 22 mm in depth which can be installed in front of the tiles but behind the face plate of the shower. This spacer is available in all the different shapes of valve that we do, square, soft cube and round.