Spoke nipple

The spoke nipple is a headed cylinder with threading on the inside through part of its length (there is an unthreaded lead-in nearest the "flats").

Standard materials for nipples are brass (usually nickel-plated) and aluminum.

Brass is heavier but more durable and less prone to corrosion, rounding of flats while tightening, breaking and galling; aluminum is far lighter.

Also, with aluminum nipples care and a good spoke wrench are needed to avoid rounding the flats while tightening.

suggest that they combine the advantages of brass and aluminum nipples (strength and weight, respectively), while being more corrosion resistant than either material.