The flats are there to provide a tacticle feature to help users properly orient their grenade before yanking on the pin. I once had a very round grenade. I noticed that users bent a lot of pins because they were frequently pulling across the pins. After a little practice, it's easy to pull inline with the pin as you remember to pull in line with the ridges.
Later models will not be needing a plastic syringe tip on the syringe. The syringe can plug right into the top of the grenade without a conical tip.
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