Fern, The Varian catalog says the SK-416 is used on the 8163 or 3-400Z. 73, Ken W2DTC __________________________________ Ken Barber Middletown, NJ Radio Website: http://w2dtc.com __________________________________ > Can someone please enlighten me as to which tube(s) the Eimac SK-416 > chimney is suitable for. Thanks from Fern