650439-X4B 2:1 Ratio, 4 1/4" Air Motor 21.3 GPM (80.6 LPM) max flow 650640-X4B 3:1 Ratio, 6" Air Motor 29.3 GPM (110.8 LPM) max flow 650639-X4B 4:1 Ratio, 6" Air Motor 21.3 GPM (80.6 LPM) max flow 650840-X4G-B 5:1 Ratio, 8" Air Motor 32.8 GPM (124.0 LPM) max flow 650839-X4G-B 7:1 Ratio, 8" Air Motor 23.5 GPM (88.8 LPM max flow