The smallest works on all my rods unless you want one on the cork then the next size up also the idea of the larger size they sell was to fasten your rod tube to a bike or pack frame...

Since I just purchased a zimmerbuilt Tenkara sling lite.. I can now carry all the of my rods n all gear needed for a day trip..so say I end up smallmouth fishing in the late morning on some bigger water then catching trout on a small trib. Later in the evening where it's much tighter I have rods to handle it all! I'm going to love this so much!!! I should have sprung for the "guide model sling but it only added a couple pockets..n way more money..