An apparatus (10) for helping to protect an occupant (20) of a vehicle (12) having a seat (16 or 22) for receiving the occupant (20) includes an inflatable protection device (14) inflatable from a stored condition in the vehicle (12) adjacent a reaction surface (19, 23, 36) to a deployed condition between the reaction surface and the vehicle occupant (20). The protection device (14) includes a front portion (62) presented toward the seat (22) and an inflatable volume for receiving a penetrating occupant (20′) when the protection device (14) is in the deployed condition. A rear portion (64) connected to the front portion (62) has an inflatable volume spaced from the front portion (62) by a space (110). The front portion (62) is positioned between the vehicle occupant (20) and the rear portion (64) when the protection device (14) is in the deployed condition. The inflated front portion (62) is movable in a fore-aft direction relative to the rear portion (64) to engage the occupant (20) regardless of the distance between the reaction surface (19, 23, 36) and the occupant (20).