stylistic:style_transfer, quality:correction
Niche uses

Applications requiring its high density include weights, counterweights, ballast keels for yachts, tail ballast for commercial aircraft, rotor weights for civil and military helicopters, and as ballast in race cars for NASCAR and Formula One. Being slightly less than twice the density, tungsten is seen as an alternative (albeit more expensive) to lead fishing sinkers. Depleted uranium is also used for these purposes, due to similarly high density. Seventy-five-kg blocks of tungsten were used as "cruise balance mass devices" on the entry vehicle portion of the 2012 Mars Science Laboratory spacecraft. It is an ideal material to use as a dolly for riveting, where the mass necessary for good results can be achieved in a compact bar. High-density alloys of tungsten with nickel, copper or iron are used in high-quality darts (to allow for a smaller diameter and thus tighter groupings) or for artificial flies (tungsten beads allow the fly to sink rapidly). Tungsten is also used as a heavy bolt to lower the rate of fire of the SWD M11/9 sub-machine gun from 1300 RPM to 700 RPM. Tungsten has seen use recently in nozzles for 3D printing; the high wear resistance and thermal conductivity of tungsten carbide improves the printing of abrasive filaments. Some string instrument strings incorporates tungsten. Tungsten is used as an absorber on the electron telescope on the Cosmic Ray System of the two Voyager spacecraft.