A second-stage regulator for scuba divers is disclosed that reduces considerably the inhalation effort required by the user through reduction in friction between selected components of the regulator. A flexible sleeve is sealingly connected to the regulator poppet and the baffle, and coaxially with the poppet, so as to avoid blow-by of gaseous mixture through an opening in the baffle. A tail of the poppet extends through the opening, the tail being connected to a lever of the regulator projecting into an outlet chamber thereof. The head of the poppet is or includes a ferrule with an at least partially-circular profile and abuts a selected inner portion of the inlets intermediate chamber to allow oscillation of the poppet. The lever end of the regulator contacts a diaphragm, the diaphragm separating the outlet chamber from the external environment. The lever end has a generally arched shape with a profile such that the length of the arch between two adjacent contact points measured along the lever is generally equal to the length of the segment between the same adjacent contact points measured along the diaphragm.
