An inflator device (10; 110; 200) for an inflatable restraint system, the inflator device (10; 110; 200) comprising: a housing (12; 112; 212, 312) at least in part defining an elongated chamber (14; 114; 214, 314) and having oppositely disposed first and second axial ends (16, 18; 116, 118; 216, 218, 316, 318), the elongated chamber (14; 114; 214, 314) containing an initial supply of stored inflation gas; an initiator (22; 122; 222, 322) disposed proximate the first axial end (16; 116; 216, 316) and an openable closure (28; 128; 228, 328) disposed proximate the second axial end (18; 118; 218, 318); and a slidable gas generator assembly (40; 140; 240, 340) disposed within the elongated chamber (14; 114; 214, 314) between the initiator (22; 122; 222, 322) and the closure (28; 128; 228, 328), the slidable gas generator including a supply of gas generant material (46; 146; 246, 346), the gas generant material (46; 146; 246, 346) reactable upon initiation to produce additional inflation gas; wherein upon actuation of the inflator device (10; 110; 200), the initiator (22; 122; 222, 322) and the slidable gas generator assembly (40; 140; 240, 340) are adapted to cooperate to create a pressure wave to open the closure (28; 128; 228, 328) and to permit release of inflation gas from the elongated chamber (14; 114; 214, 314) and at least a portion of the supply of the gas generant material (46; 146; 246; 346) reacts to form said additional inflation gas; characterized in that the slidable gas generator assembly (40; 140; 240, 340) comprises a downstream slidable open top cup-shaped baffle (42; 142; 242, 342) spaced apart from an upstream end baffle (44; 144; 244, 344) and includes said supply of gas generant material (46; 146; 246, 346) disposed between said baffles. a housing (12; 112; 212, 312) at least in part defining an elongated chamber (14; 114; 214, 314) and having oppositely disposed first and second axial ends (16, 18; 116, 118; 216, 218, 316, 318), the elongated chamber (14; 114; 214, 314) containing an initial supply of stored inflation gas; an initiator (22; 122; 222, 322) disposed proximate the first axial end (16; 116; 216, 316) and an openable closure (28; 128; 228, 328) disposed proximate the second axial end (18; 118; 218, 318); and a slidable gas generator assembly (40; 140; 240, 340) disposed within the elongated chamber (14; 114; 214, 314) between the initiator (22; 122; 222, 322) and the closure (28; 128; 228, 328), the slidable gas generator including a supply of gas generant material (46; 146; 246, 346), the gas generant material (46; 146; 246, 346) reactable upon initiation to produce additional inflation gas; wherein upon actuation of the inflator device (10; 110; 200), the initiator (22; 122; 222, 322) and the slidable gas generator assembly (40; 140; 240, 340) are adapted to cooperate to create a pressure wave to open the closure (28; 128; 228, 328) and to permit release of inflation gas from the elongated chamber (14; 114; 214, 314) and at least a portion of the supply of the gas generant material (46; 146; 246; 346) reacts to form said additional inflation gas; characterized in that the slidable gas generator assembly (40; 140; 240, 340) comprises a downstream slidable open top cup-shaped baffle (42; 142; 242, 342) spaced apart from an upstream end baffle (44; 144; 244, 344) and includes said supply of gas generant material (46; 146; 246, 346) disposed between said baffles.