A mounting apparatus for mounting a removable module in a chassis with a sidewall defining a locking slot includes a locking member, and an operation member. The pressure-limiting valve comprises a valve support, a valve insert which is connected to the valve support, a valve piston which is mounted such that it can slide in the valve insert, and a closing spring which acts on the valve piston with a closing force in the closing direction. A series of vapor permeation membranes retain ethanol as retentate and produce a 99 wt % or higher ethanol product. More particularly, the first metal is selected so as to provide a superior bone-engaging face, while the second metal is selected so as to provide a superior polyethylene-engaging face. The axis of emission diverges in the emission direction from the axis of reception at an angle of at least two degrees. When the distance by which the base plate 11 and the laser section 8 are spaced apart is a predetermined value or more, heat transmitted to the laser section 8 can be effectively blocked.