Flux deposition is effected in mass production through fluxer units. In modern wave soldering systems, the use of spray fluxers is more or less standard. Spray fluxers deposit the flux, similar to spray pistols, in small volumes in a very fine spray evenly on the underside of the pcb. Multidrop fluxers are used in selective soldering systems. Their operating principle is that of inkjet printers. They do not atomise the flux, so precise fluxing of the smallest quantities is possible. In manual hand- and repair soldering, flux is delivered to the joint to be made in either flux pens, paste form, or as a core in the solder wire.