Abstract: A pressure indicator for use in a pneumatic circuit. A rolling diaphragm (14) is mounted within a housing (9,10) and divides the housing into first and second regions (15,16), one sealed from the other. The diaphragm has an outer sleeve section (18) and a connected inner cup section (19) lying within the outer sleeve section, the outer surface of the cup section and the inner surface of the sleeve section both being subject to pressure in the second region. An indicator (22) is seated within the cup section. The cup section is biased towards the first region against pressure therein, and into a position wherein the indicator lies substantially wholly within the cup section and is shielded from view thereby. The housing has a transparent section through which the indicator may be viewed as it moves out of the cup section in response to increasing pressure differential between the first and second regions.