The plastic version of this umbrella rib tip was tested on fiber glass ribs with a diameter of 3.0mm (please measure your umbrella's rib with a calliper before you buy this product, it may not fit!).
Strong & flexible as well as transparent detail fits perfectly and replace a sew-in tip if you have lost one, but wear&tear of the plastic versions is poor (they will break after a few weeks or months is used repeatedly) - I strongly advise you get a steel or other metal version.
The steel version is strong but the inner diameter comes out smaller, it fits a 2.5 or 2.6mm rib.
For the 3mm version see my ever so slightly larger version (link to be updated soon, after testing complete).
My umbrella, as seen on photo, was made by H.DUE.O but is not on catalogue any longer. Different umbrellas will have different rib diameters. The main photograph shows the original tips (O), the iron print (I) and the transparent detail print (T).