Abstract: The present invention, includes: a damper unit provided between an airbag module that acts as a damper mass for a steering wheel and the steering wheel to dampen vibrations of the steering wheel, an engagement mechanism provided in the airbag module that maintains the airbag module on the steering wheel in a relatively displaceable manner, and protecting means provided on the airbag module for stopping external forces to the engagement mechanism in a non-engaged state with the steering wheel, that may cause deformation, and thereby protecting the engagement mechanism.

Abstract: A hollow fiber membrane, wherein an inner diameter (Id) is within the range of 100 to 200 &mgr;m, the ratio (Mt/Id) of a wall thickness (Mt) to the inner diameter (Id) is the range of 0.9 to 1.1, a bubble point (Bp) is at least 0.5 MPa, and the ratio (Di/Do) of the maximum major axis (Di) of the pores existing in the layer of up to 10 &mgr;m thick from an inner surface to the maximum major axis (Do) of the pores existing in the layer of up to 10 &mgr;m thick from an outer surface is within the range of 10.0 to 15.0; a hollow fiber membrane module formed of the hollow fiber membranes; and a water purifier formed of the hollow fiber membrane module.