An inflatable safety device

An inflatable safety arrangement for a safety device in a motor vehicle, especially an in-seat device to prevent "submarining" comprises an inflatable unit (10) formed of at least one pre-formed plastically deformable element (13) which initially defines an inwardly directed recess (14) partially filling a void defined within the interior of the inflatable unit (10). On actuation of a gas generator the inwardly directed protrusion (14) becomes an outwardly directed protrusion. The inwardly directed protrusion (14) may have two substantially planar walls (15, 16), one of which carries an outwardly extending projection (19).