I was so happy with the 100 ml briki! So I ordered this larger ~170 ml version for when I want to brew slightly larger cups and for sharing. Getting the brew ratio right can be important for specific beans, roasts and the like. Having a couple of different sizes gives greater flexibility. I can use the 100 and 170 on the micro burner or the slightly larger Kovea 8911-1 gas stove. The shape and weight are just right to control the extraction and preparation (using the wrap and crema color method). Currently the cevze and Turkish coffee method are my go-to for each new bean and roast I order, and as a reference point when comparing different coffees.
That is for sure the most reasonable size (170 ml). I use 250 ml and sometimes it feels a little bit bulky. While 100 ml is always fun. And perfect for testing, how the foam should be wrapped to transfer the recipe to a bigger one.