... frame without "P"504 is the code for wire feed frame we have 21,401,402,404,501 ... K,Three types,"V"fit to steel wire ,"U"fit to fluxcore wire an "K"fit to aluminium wire0. ... 8/1.0 is the trough dimension of roll , ... your welding wire size. Our standard feed-roll size:0.6/0.8,0.8/0.9,0.8/1.0,1.0/1.2, ... 1.2/1.6,1.6/2.0,2.0/ ...