I’ve consolidated the regular brass and aluminum nipples in one product listing because they’re the same design (Polyax). At the same Sapim hex nipples were added to the shop.

What is hex about? Hexagonal head nipples have an additional wrench surface on the rear. With more contact points and a larger contact surface, higher torque is permitted. Higher torque can help free seized nipples down the road and keeps the finish of the front tool flats pristine when building in the first place. Some wheelbuilders may find the wrench turning direction more intuitive from the rear however hex drive nipples retain regular wrench flats for day-to-day truing as needed.