Heat-resistant block, refractory ring, or hollow
sheet-metal box, 150 to 175 mm in diameter if round, or on
a side if square, 32 to 38 mm in thickness, provided with a
metal-lined, inverted cone-shaped opening through the center;
83 mm in diameter at the bottom, and 89 mm in diameter at the
top. In the case of the refractory ring no metal lining is
necessary, providing the ring is of hard, heat-resistant material
Burner, Meker type, having an orifice approximately 24
mm in diameter.