The main disadvantage of storage tubes is that once the image is stored, it can only be removed by erasing the entire image. This makes this display unsuitable for working with scrolling text, animation, or any other display where portions of the image are changing. Tek introduced the "write through" concept for non-stored vectors, but, with the terminal itself lacking any memory, these had to be continually refreshed by the host computer. This limited the number of these objects to the communications speed of the connection between the terminal and host, and was often in the low dozen range. Another disadvantage is that it takes a short time for the image to stick on the display, which limits the speed that the image can be drawn. Tektronix referred to this as the "stored writing speed", and measured it in terms of vector-inches-per-second, with numbers between 1500 and 4000 being typical for their displays.