Hi, my Romac book says they are 2' 1" long for 1946, and then went to 2' 3" for 1947 and the M33 also used a 2' 3" . The Romac cable number is AS102 for 1946 and for 1947 it is AS103 the inners are numbered W2 which is 2'1" long and W3 which is 2'3" respectively and are both square ended. The outer has a hexagon on the bottom and a knurled ring on the top.