These Plastic Cup Diaphragms help prevent paint from entering the spray gun through the pressure tube.
Tough and durable, the diaphragms should last
months (if not years) if care is taken sliding
them down the metal fluid tube. To remove
them from the cup, grab the tab. The air
hole in the diaphragm should be positioned
at the rear of the cup (towards the handle).
That is, unless you intend spraying upwards
for any length of time. For spraying upwards,
position the hole in the diaphragm towards
the front of the spray gun. The idea is to
keep the hole out of the paint as much as
possible. These diaphragms, in combination
with the pressure tube/check valve, cure
the problem of paint backing up the pressure