In some cases ... yes. The largest nominal size is 1-1/4" OD. Stainless rails are typically manufactured from tubing, which is specified by Outside Diameter. Most aluminum boat builders use pipe instead of tubing, which is specified by Inside Diameter. One of the most common pipe sizes used is 1" pipe (usually what is called 'Schedule 40' specification pipe) which ends up with an Outside Diameter of 1.30" ... just small enough for the RK300 rail kit to work in most cases.