3LNB has only one white LNB and the 5LNB has three white LNB's on it. You could also check you receiver, the auto setup should detect what you have and if you look at the INFO selection under setup you'll see. Another way if you have the 5LNB you'll have sats 101/110/119/99(c)/99(s)/103(s)/103(c), the 3LNB won't have 119 and 110. Does it matter, only if you're missing some channels that you should be receiving, maybe your SD locals or some international programming packages.