up to 11mm diameter (fits most thin rods).
up to 13.2mm diameter (fits most rods).
up to 15.3mm diameter (fits you thicker rods).
up to 18.3 diamerter (fits some Keiryu rods).
I love the Universal Tip Cap because it is more functional than the traditional rod tip plugs. They hold very securely and do not slide off on accident. You can keep your line attached to the rod with out it getting pinched by a rod plug. And most people find them harder to loose track of.
I use the Universal Rod Tip Caps on most of my rod and I think you will love them as well.