The UPG-300/UPG-300 NGZh-4 mobile hydraulic systems are housed in a special car body mounted on the ZiL-131N cross-country chassis. They are designed to check and adjust aircraft hydraulic systems in field conditions, either with or without hydraulic tank pressurisation.

The systems comprise three separate main hydraulic systems, which can simultaneously provide pressure to three separate aircraft systems or can be combined to provide hydraulic pressure to one or two aircraft systems.

The hydraulic systems use the AMG-10/7-50s- 3/NGZh-4 hydraulic fluids pressurised to 5-21 MPa. The flow rate for each of the three hydraulic systems is 20-70 l/min.