Argal reversible models, namely “R” type, answer to the market demand for compact, practical and economical pumps of limited flow.Those features are obtained departing from the traditional design where the liquid is pumped through manifolds external to the opposite chambers by diaphragms motioned by an air actuated motor located in between, for a new architecture where liquid flows through a straight central section, manifolds are eliminated with the associated cost and hydraulic losses, and the overall dimensions of the pump are reduced.