When determining the length of a grab bar needed, keep in mind that the overall length of the grab bar is about 3 inches longer (3.125 - 3.25 inches depending on the style of bar) than the name of the bar. So a 42 inch grab bar would measure about 45 inches end to end with the points for attachment 42 inches apart.
42 inch grab bars are a popular choice in bigger bathrooms or in commercial bathrooms that require a minimum of a 42 inch bar adjacent the toilet. While installation into studs is always ideal, state of the art Snaptoggles and Secure Mount Anchors can make any installaltion in a hollow wall easy even if you can't locate the studs. All of our 42 inch grab bars meet or exceed ADA guidelines for safety in the bathroom.