Here’s one concession to economics. Sometimes you may be allowed to use titanium retainers, but these are steel. The titanium units are lighter but they are quite a bit more costly and wear out more quickly. Some new coating processes help increase the lifespan of titanium retainers, but that only adds to the cost. Well made steel retainers, however, don’t add significantly to the overall valvetrain weight. No matter which you use, do make sure that the retainer fits the spring tightly and that there are no sharp edges on the spring where it contacts the retainer, which can lead to a failure.