Our tower bases allow for Down River's Oar Tower to fit in the vertical plane. The horizontal plane allows for two sizes of aluminum pipe, 1.5" pipe (measures 1 7/8" O.D.) as well as 1.25" pipe (1 5/8" O.D.).
The size of pipe used is not only referenced by it's inside diameter among industry professionals, but that same size designation is used when referencing the appropriate size structural fittings. Example; If you're pipe measures 1 7/8", then it will commonly be refered to as 1.5" pipe and you will also need to shop for 1.5" fittings as well.
If your measurements seem close but not quite on the money, aren't sure what you should be measuring, or just need to double check with us that you're ordering the right part, please call or e-mail us anytime. We would be happy to answer any questions.