The part number guide shown here demonstrates how Qualtek Electronics distinguishes each filter using the part number guide. The first three numbers represent the EMI Filter Series. This can mean a variety of things, from snap-in mounts to switched / fused surface mount EMI filters. The second group of numbers, the two before the backward slash ( / ) is the AMP rating of the EMI Filter; 03 = 3A (amps), 06 = A, etc. The last group of numbers, the three after the backward slash indicates the style of EMI filter, ranging from terminals to voltage selector switches. Qualtek offers a very large variety of EMI Filters and has the ability to make a custom one to fit the customers need.