They are difficult to measure exact but it looks like the rim tube OD is 21 inches. I pictured inside & outside as a guide. WE MAKE EVERY ATTEMPT TO LIST EACH ITEM AS ACCURATELY AS POSSIBLE.This item is in the category "Health & Beauty\Medical & Mobility\Mobility/Walking Equipment\Wheelchairs". The seller is "traceylynnescollectibles" and is located in this country: US. This item can be shipped to United States.