The invention provides methods for making copolymers and multi-arm block copolymers useful as drug delivery vehicles. The golf shaft has a generally tapered shape in which the outer diameter generally increases gradually from the tip portion to the butt portion. A retaining member is operably engageable with the retaining surface, and the retaining member has an orientation member preventing incorrect orientations between the retaining member and the housing. A corresponding control signal is generated, and provided to a variable attenuator in order to maintain the individual output channel power level at or below the maximum output signal level. A number of premixed combustion gas burners each having an identical output capacity of the burner, are disposed in parallel with one another and a number of operating burners is varied according to a desired calorie.