DT's standard Pro Lock nipples feature a coating on the threads that delivers two primary benefits. Because the coating eliminates metal on metal contact, spokes will tension up more smoothly without the spoke prematurely binding or twisting before it is up to full tension. Our wheel builders strongly prefer Pro Lock nipples particularly for builds with black spokes and black nipples where binding can be a problem. Tension and trueness are also better maintained through the life of the wheel with Pro lock nipples.
Brass (versus alloy) is the best choice for strength, high spoke tension and corrosion resistance. Brass nipples resist rounding and cracking better than alloy nipples but are about .6 grams heavier per nipple.