For me, the best shafts are made of carbon. It's durable and lightweight. The tips can be glued on well and the silicone hoses hold up well. The carbon shafts are what wear out the least for me. My carbon shafts have a diameter of 2.5 mm and are all exactly 15.5 cm long.
In order to always find the same size without much effort, I cut off a brass tube. The brass tube is 16 cm long. I glued a piece of a nail 0.5 cm long into the lower end. This closes part of the tube in this way. Carbon rods are always delivered by the meter. If I now insert a carbon rod into this tube, I can use a cutter knife to cut off the future shaft exactly at the edge of the tube. This is easy and absolutely repeatable.