ST1 Spray Gun ST1 SPRAY GUN Standard ST1 Spray Guns are fitted with the traditional Power-Sprays slotted nozzle assembly, which injects the air just behind the spray tip. Alternatively, Power-Sprays MAM system (Minimum Air Mix) can be supplied as an optional extra. The MAM system injects the air through small holes in the spray tip, which improves atomisation. The Power-Sprays ST1 Spray Gun is designed for the smooth application of facing coats on GRC panels and other cement based materials.