Current technology uses blades fabricated almost completely of composites. The weights permit the designer to better tailor the blade's flight characteristics and control feedback forces. They also allow the blades to be balanced with respect to each other at installation on a given aircraft. The abrasion strip is often replaceable, so that the whole blade does not need to be replaced because of its most obvious sign of wear. If hydraulic powered controls are used, control force is less important, and non-symmetrical airfoils are often employed to maximize lifting efficiency.
Some blades also employ twisting along their length, again to optimize lifting efficiency.