Generac Air Filter Plus Pre-Filter Air Filter 78601, 078601, 78601GS, 178601GS, 078601GS. Pre-Filter 78602, 078602 Quality Aftermarket Air Filter Plus Pre-Filter Air Filter Replaces Generac 78601, 078601, 78601GS, 078601GS, 178601GS Pre-Filter Replaces Generac 78602, 078602 Width: 3-1/4", Length: 6", Height: 1"