The size of your shower and the location of your drain will determine how long your linear shower drain should be. These two considerations must be taken into account to ensure that the end is put at a uniform distance from both walls and covers less than eight to ten cm on each side. A linear shower drain must be the same length as the distance between walls and at least 4 inches on all sides when installed wall to wall. A linear shower drain should not exceed the distance between two neighboring walls. The specs for linear shower drain installation are available on the manufacturer's website. To properly install without causing any property damage, it would be helpful to read the instructions beforehand.