The flow rate of a formulation through hand‐held u.l.v. equipment is determined by the viscosity of the product and the diameter of the restrictor orifice fitted. A convenient flow rate onto the atomiser head is 1 ml s−1. Most hand‐held u.l.v. equipment is supplied with several interchangeable restrictors allowing the spray operator to choose one suitable for the formulation to be applied. The flow rates of four blank (containing no pesticide) u.l.v. formulations, each of different viscosity, through five different pieces of application equipment were investigated. The results are tabulated so that the spray operator can choose an appropriate restrictor to fit to the hand‐held u.l.v. equipment he wishes to use. To use this information the operator must know the viscosity of the product at the temperature he intends to spray at It should be emphasised that the results presented in no way eliminate the need for a calibration run before commencing spraying.