A seat belt retractor (10) has an actuator (14) for unlocking and locking the seat belt retractor (10). An inertial sensor (18) detects changes in vehicle acceleration and interacts with the actuator (14) to lock and unlock the seat belt retractor (10). The inertial sensor (18) has one inertial sensor mass, each mass (26, 27, 29, 30, 32, 33) has a wide portion (70) and a narrow portion (72). Preferably each inertial sensor mass (26, 27, 29, 30, 32, 33) has a high density body (31) embedded in the wide portion (70) of the elastomeric material (34). The inertial sensor mass (26, 27, 29, 30, 32, 33) has a greater density than the elastomeric material (34). Moreover, the elastomeric material (34) at least partially surrounds an exterior circumferential surface (38) of the inertial sensor mass (26, 27, 29, 30, 32, 33). The inertial sensor mass (26, 27, 29, 30, 32, 33) has a body (31) having the wide portion (70) and optionally the narrow portion (72) with preferably one or more elastomeric protruding member (54, 58) extending from said body (31). The one or more protruding members (55, 58) are movable relative to said body (31) and soften contact rattle impacts thus reducing noise.