Bed rails are not necessarily universal, as there are different types of beds and bed frames that may require different types of bed rails. 

When purchasing bed rails, it is important to ensure that they are compatible with the specific bed and bed frame that they will be used with. Some bed rails are designed to be adjustable and can fit a range of bed sizes, while others may be more specific to certain bed sizes or styles. 

It is also important to consider the weight and height of the person who will be using the bed rails, as some bed rails may not be suitable for heavier individuals or may not be tall enough to provide effective protection against falls. 

Before purchasing bed rails, it may be helpful to consult with a healthcare provider or a specialist in home safety equipment to ensure that you are selecting the appropriate type of bed rails for your specific needs and circumstances.