Studies were conducted at the water management Research Unit (sub centre of ARS, chalakudy), Kerala Agricultural University, Vellankkara for the selection of optimal size of KAU micro sprinkler (one unit of which was developed earlier at ARS, Chalakudy). The studies helped to develop affordable, dependable, simple and farmer friendlylow cost micro sprinklers (KAU micro sprinklers) suitable for various crops. KAU micro sprinkler irrigation system is comparatively cheaper (<` 2/-) than drip and commercially available micro sprinklers. Moreover, this system was designedto operate clog free with complete wetting of the basin area (> 90%) of the crop due to its rotating action. It is found intermediary between the drip and sprinkler system in discharge rate (35l to 76 l) and effective wetting radius (1.65 m to 0.5 m). The performance of KAU micro sprinklers was evaluated by observing effective wetting radius, discharge rates, water distribution pattern and coefficient of variation. The study revealed that length to diameter ratio (L/D ratio) of the KAU micro sprinkler heads had considerable influence on the discharge and water distribution characteristics. Amongdifferent diameter ( i.e. with 8 mmf , 12 mmf and 16 mmf) sprinkler heads, the unit having medium L/D ratio gave better performance.