I was going to go with a .204" (5mm) arrow but I was talking to someone I trusted they said why go with the .166" and since i couldn't find the ones I was looking for I said what the heck. So far I am impressed with my bow and these arrows but it doesn't take much when I went from a 2005 PSE Firestorm Lite (30" ATA) and Gold tip XT hunters to a 2021 PSE EVO EVL (34" ATA) and Black Eagle X-Impacts. I was tossing between the GT Airstrike and the BE X-Impact since I couldn't find the Victory RIP TKO.