The glue supply unit with diaphragm pump is designed for use with low viscosity glue. The diaphragm pump has a 1:1 ratio (1 bar air pressure on the pump gives 1 bar glue pressure).
The glue supply unit with piston pump is designed for use with low viscosity glue. The piston pump has a 1:4 ratio (1 bar air pressure on the pump gives 4 bar glue pressure).