The first effective micro systems were a response to the demand for a low application system which "spread" water over a greater area. Bowsmith's fan jet was the leader for many years, while the spin type micro sprinkler just did not hold up.

Today spinners, jets and the nelson R-5 are widely accepted and usually designed for trees at one or sometimes two per tree.  Higher maintenance than either drip or sprinklers, the systems are mid range in regard to price.