A burner tube consisting of a length of stainless steel tube [ ( 8 土 0 , 1 ) mm outside diameter ,( 6 , 5 土 0 , 1 〕 mm internal diameter and ( 200 ± 5 ) mm in length ] is connected by flexible tubing to a cylinder containing butane via a flowmeter , fine control valve , on - off valve ( optional ) and cylinder regulator providing outlet pressure of nominal 2 , 8 kPa 1 )