We can not guarantee the removal of certain stains.
Sometimes rust comes off of porcelain, other times it has chemically bonded and is impossible to remove.
Another problem in The Vegas Valley is the Hard water.
In almost every case, we can break free the mineral deposits from shower glass, but there are buildup levels that again,
NO chemical can clean fully without etching the glass.
Soap Scum is another tough stain to remove.
If the shower stall or bathtub is plastic-stains are usually permanent and it is best to replace it.