Ken -
Let us know what the real bore diameter is. They said 107mm (4.6") but by my calculations (1.000" is EXACTLY equal to 25.4mm) that's 4.2".
107mm cannon ball in 4.6" diameter bore maybe?
In any event the 4" pvc pipe is 4.500" in diameter if you're looking for cheap containers to fill with concrete. (Won't go as far as heavier,denser cast zinc or cast iron spheres, though).