Usually this size is based on the size of common bathtub, because the function of this curtain rod is not only for shower but it can also be used for bathtub. One of the most wanted shower curtain rod that is easy to be installed is L shaped shower curtain rod. This kind of curtain rod curves 90 degree and needs to be attached to the wall on both ends of the rod. This curtain rod is not only for shower only, but also for bathtub or bathtub and shower stall. Bathroom.